Express Yourself<\/h1>\r\n<\/div>\r\nThis sketch illustrates some of the variability in human\u00a0[pb_glossary id=\"5665\"]cells[\/pb_glossary]. The shape and other\u00a0characteristics\u00a0that make each type of cell unique depend mainly on the\u00a0specific\u00a0proteins\u00a0that particular cell type makes. Proteins are encoded in genes. All the\u00a0cells\u00a0in an organism have the same genes, so they all have genetic instructions for the same proteins. Obviously, different types of cells must use (or express) different genes to make different proteins.\r\n\r\nWhat Is Gene Expression?<\/h1>\r\n<\/div>\r\nUsing a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a\u00a0[pb_glossary id=\"5813\"]protein[\/pb_glossary]\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] of [pb_glossary id=\"277\"]DNA[\/pb_glossary] into [pb_glossary id=\"2212\"]mRNA[\/pb_glossary],\u00a0 and [pb_glossary id=\"2242\"]translation[\/pb_glossary] of mRNA into a protein. It may also include further processing of the protein after synthesis.\r\n\r\nGene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in [pb_glossary id=\"1573\"]eukaryotic[\/pb_glossary]\u00a0cells, and it is the focus of this concept.\r\n\r\nRegulation of Transcription<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_2407\" align=\"alignright\" width=\"718\"]![\"\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Activators-and-Repressors-2.png\")
Figure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em>[\/caption]\r\n\r\nAs shown in Figure 5.9.2, transcription is controlled by [pb_glossary id=\"2402\"]regulatory proteins[\/pb_glossary]<\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0[pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary]<\/strong>, which are located near promoters. The [pb_glossary id=\"2404\"]promoter[\/pb_glossary] is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to [pb_glossary id=\"2212\"]mRNA[\/pb_glossary]. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0[pb_glossary id=\"2405\"]Activators[\/pb_glossary]<\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0[pb_glossary id=\"2406\"]Repressors[\/pb_glossary]<\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.\r\n\r\n \r\n\r\n\r\nEnhancers<\/span>\r\n\r\n<\/div>\r\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene's promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.[pb_glossary id=\"2409\"]Enhancers[\/pb_glossary]\r\nThe TATA Box<\/h2>\r\nDifferent types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0[pb_glossary id=\"2410\"]TATA box[\/pb_glossary]<\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.\r\n\r\n[caption id=\"attachment_2450\" align=\"aligncenter\" width=\"886\"]![\"Components](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/TATA_box_description-2.png\")
Figure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em>[\/caption]\r\n\r\n\r\nRegulation During\u00a0Development<\/h1>\r\n<\/div>\r\nThe\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism's early\u00a0development. Regulatory proteins must \"turn on\" certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.\r\n\r\n[pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary]<\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0[pb_glossary id=\"5983\"]embryonic[\/pb_glossary] stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0[pb_glossary id=\"5707\"]amino acids[\/pb_glossary], called\u00a0[pb_glossary id=\"2413\"]homeodomains[\/pb_glossary]<\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.\r\n\r\nGene Expression and\u00a0Cancer<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_2416\" align=\"alignleft\" width=\"315\"]![\"This](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/pathways-to-cancer-2.png\")
Figure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em>[\/caption]\r\n\r\nSome types of [pb_glossary id=\"5605\"]cancer [\/pb_glossary]occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.\r\n\r\n \t- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car's accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n \t
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can't be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n<\/ul>\r\n \r\n\r\n \r\n\r\n
\r\n5.9 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Using a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a [pb_glossary id=\"5813\"]protein[\/pb_glossary] is called [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0[pb_glossary id=\"2210\"]protein synthesis[\/pb_glossary]\u00a0or processing.<\/li>\r\n \t
- The regulation of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] is controlled by [pb_glossary id=\"2402\"]regulatory proteins [\/pb_glossary]that bind to regions of DNA called [pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary], which are usually located near [pb_glossary id=\"2404\"]promoters[\/pb_glossary]. Most regulatory proteins are either [pb_glossary id=\"2405\"]activators[\/pb_glossary] that promote transcription, or [pb_glossary id=\"2406\"]repressors[\/pb_glossary] that impede transcription.<\/li>\r\n \t
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\r\n \t
- Regulation of gene expression\u00a0is extremely important during an organism's early development. [pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary] \u2014 which encode for chains of\u00a0amino acids\u00a0called [pb_glossary id=\"2413\"]homeodomains[\/pb_glossary] \u2014 are important genes that regulate development.<\/li>\r\n \t
- Some types of [pb_glossary id=\"5605\"]cancer[\/pb_glossary] occur because of\u00a0[pb_glossary id=\"2381\"]mutations[\/pb_glossary]\u00a0in the genes that control the\u00a0[pb_glossary id=\"5643\"]cell cycle[\/pb_glossary]. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Define gene expression.<\/li>\r\n \t
- Why must gene expression be regulated?<\/li>\r\n \t
- Explain how regulatory proteins may activate or repress transcription.<\/li>\r\n \t
- [h5p id=\"503\"]<\/li>\r\n \t
- What is the TATA box, and how does it work?<\/li>\r\n \t
- Describe homeobox genes and their role in\u00a0an organism's development.<\/li>\r\n \t
- Discuss the role of regulatory gene mutations in cancer.<\/li>\r\n \t
- Explain the relationship between proto-oncogenes and oncogenes.<\/li>\r\n \t
- If a newly fertilized egg contained a\u00a0mutation\u00a0in a homeobox gene,\u00a0how do you think this would affect the developing embryo? Explain your answer.<\/li>\r\n \t
- Compare and contrast enhancers and activators.<\/li>\r\n<\/ol>\r\n \r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Explore More<\/strong><\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?time_continue=3&v=vi-zWoobt_Q&feature=emb_logo\r\nRegulated Transcription, ndsuvirtualcell, 2008.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan,\r\nTED-Ed, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE\r\n
What is leukemia? - Danilo Allegra and Dania Puggioni, 2015.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 5.9.1<\/strong>\r\n\r\nStem_cell_differentiation.svg<\/a> by Haileyfournier<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.2<\/strong>\r\n\r\nActivators and Repressors by Christine Miller is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.3<\/strong>\r\n\r\nTATA_box_description<\/a> by Luttysar<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.4<\/strong>\r\n\r\nPathways to cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n\r\n![\"\"](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/logo_ck12.png\")
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span>![\"CK-12](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/icon_licence.png\" "\\"CK-12")
<\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\r\n\r\n \r\n\r\nReferences<\/span>\r\nBrainard, J\/ CK-12 Foundation. (2012). Figure 3 Flow chart (series of mutations leading to cancer) [digital image]. In CK-12 College Human Biology <\/em>(Section 5.8) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/c\/physical-science\/concentration\/?referrer=crossref<\/span><\/p>\r\nndsuvirtualcell.(2008). Regulated transcription. YouTube. https:\/\/www.youtube.com\/watch?v=vi-zWoobt_Q&feature=youtu.be<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, April 15). What is leukemia? - Danilo Allegra and Dania Puggioni. YouTube. https:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE&feature=youtu.be<\/p>","rendered":"
<\/p>\n![\"Shows](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Stem_cell_differentiation.svg_-2.png\")
Figure 5.9.1 Differentiation pathways for a stem cell based on gene regulation. <\/em><\/figcaption><\/figure>\n\nExpress Yourself<\/h1>\n<\/div>\n
This sketch illustrates some of the variability in human\u00a0cells<\/a>. The shape and other\u00a0characteristics\u00a0that make each type of cell unique depend mainly on the\u00a0specific\u00a0proteins\u00a0that particular cell type makes. Proteins are encoded in genes. All the\u00a0cells\u00a0in an organism have the same genes, so they all have genetic instructions for the same proteins. Obviously, different types of cells must use (or express) different genes to make different proteins.<\/p>\n\nWhat Is Gene Expression?<\/h1>\n<\/div>\n
Using a gene<\/a> to make a\u00a0protein<\/a>\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of transcription<\/a> of DNA<\/a> into mRNA<\/a>,\u00a0 and translation<\/a> of mRNA into a protein. It may also include further processing of the protein after synthesis.<\/p>\nGene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in eukaryotic<\/a>\u00a0cells, and it is the focus of this concept.<\/p>\n\nRegulation of Transcription<\/h1>\n<\/div>\nFigure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em><\/figcaption><\/figure>\nAs shown in Figure 5.9.2, transcription is controlled by regulatory proteins<\/a><\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0regulatory elements<\/a><\/strong>, which are located near promoters. The promoter<\/a> is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to mRNA<\/a>. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0Activators<\/a><\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0Repressors<\/a><\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.<\/p>\n <\/p>\n
\nEnhancers<\/span><\/p>\n<\/div>\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene’s promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.Enhancers<\/a><\/p>\nThe TATA Box<\/h2>\n
Different types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0TATA box<\/a><\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.<\/p>\nFigure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em><\/figcaption><\/figure>\n\nRegulation During\u00a0Development<\/h1>\n<\/div>\n
The\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism’s early\u00a0development. Regulatory proteins must “turn on” certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.<\/p>\n
Homeobox genes<\/a><\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0embryonic<\/a> stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0amino acids<\/a>, called\u00a0homeodomains<\/a><\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.<\/p>\n\nGene Expression and\u00a0Cancer<\/h1>\n<\/div>\nFigure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em><\/figcaption><\/figure>\nSome types of cancer <\/a>occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.<\/p>\n\n- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car’s accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can’t be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n<\/ul>\n
<\/p>\n
<\/p>\n
\n\n\n5.9 Summary<\/span><\/h1>\n<\/header>\n\n\n- Using a gene<\/a> to make a protein<\/a> is called gene expression<\/a>. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0protein synthesis<\/a>\u00a0or processing.<\/li>\n
- The regulation of transcription<\/a> is controlled by regulatory proteins <\/a>that bind to regions of DNA called regulatory elements<\/a>, which are usually located near promoters<\/a>. Most regulatory proteins are either activators<\/a> that promote transcription, or repressors<\/a> that impede transcription.<\/li>\n
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\n
- Regulation of gene expression\u00a0is extremely important during an organism’s early development. Homeobox genes<\/a> \u2014 which encode for chains of\u00a0amino acids\u00a0called homeodomains<\/a> \u2014 are important genes that regulate development.<\/li>\n
- Some types of cancer<\/a> occur because of\u00a0mutations<\/a>\u00a0in the genes that control the\u00a0cell cycle<\/a>. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.9 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define gene expression.<\/li>\n
- Why must gene expression be regulated?<\/li>\n
- Explain how regulatory proteins may activate or repress transcription.<\/li>\n
- \n\n
What Is Gene Expression?<\/h1>\r\n<\/div>\r\nUsing a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a\u00a0[pb_glossary id=\"5813\"]protein[\/pb_glossary]\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] of [pb_glossary id=\"277\"]DNA[\/pb_glossary] into [pb_glossary id=\"2212\"]mRNA[\/pb_glossary],\u00a0 and [pb_glossary id=\"2242\"]translation[\/pb_glossary] of mRNA into a protein. It may also include further processing of the protein after synthesis.\r\n\r\nGene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in [pb_glossary id=\"1573\"]eukaryotic[\/pb_glossary]\u00a0cells, and it is the focus of this concept.\r\n\r\nRegulation of Transcription<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_2407\" align=\"alignright\" width=\"718\"] Figure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em>[\/caption]\r\n\r\nAs shown in Figure 5.9.2, transcription is controlled by [pb_glossary id=\"2402\"]regulatory proteins[\/pb_glossary]<\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0[pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary]<\/strong>, which are located near promoters. The [pb_glossary id=\"2404\"]promoter[\/pb_glossary] is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to [pb_glossary id=\"2212\"]mRNA[\/pb_glossary]. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0[pb_glossary id=\"2405\"]Activators[\/pb_glossary]<\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0[pb_glossary id=\"2406\"]Repressors[\/pb_glossary]<\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.\r\n\r\n \r\n\r\n\r\nEnhancers<\/span>\r\n\r\n<\/div>\r\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene's promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.[pb_glossary id=\"2409\"]Enhancers[\/pb_glossary]\r\nThe TATA Box<\/h2>\r\nDifferent types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0[pb_glossary id=\"2410\"]TATA box[\/pb_glossary]<\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.\r\n\r\n[caption id=\"attachment_2450\" align=\"aligncenter\" width=\"886\"] Figure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em>[\/caption]\r\n\r\n\r\nRegulation During\u00a0Development<\/h1>\r\n<\/div>\r\nThe\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism's early\u00a0development. Regulatory proteins must \"turn on\" certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.\r\n\r\n[pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary]<\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0[pb_glossary id=\"5983\"]embryonic[\/pb_glossary] stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0[pb_glossary id=\"5707\"]amino acids[\/pb_glossary], called\u00a0[pb_glossary id=\"2413\"]homeodomains[\/pb_glossary]<\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.\r\n\r\nGene Expression and\u00a0Cancer<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_2416\" align=\"alignleft\" width=\"315\"] Figure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em>[\/caption]\r\n\r\nSome types of [pb_glossary id=\"5605\"]cancer [\/pb_glossary]occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.\r\n\r\n \t- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car's accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n \t
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can't be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n<\/ul>\r\n \r\n\r\n \r\n\r\n
\r\n5.9 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Using a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a [pb_glossary id=\"5813\"]protein[\/pb_glossary] is called [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0[pb_glossary id=\"2210\"]protein synthesis[\/pb_glossary]\u00a0or processing.<\/li>\r\n \t
- The regulation of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] is controlled by [pb_glossary id=\"2402\"]regulatory proteins [\/pb_glossary]that bind to regions of DNA called [pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary], which are usually located near [pb_glossary id=\"2404\"]promoters[\/pb_glossary]. Most regulatory proteins are either [pb_glossary id=\"2405\"]activators[\/pb_glossary] that promote transcription, or [pb_glossary id=\"2406\"]repressors[\/pb_glossary] that impede transcription.<\/li>\r\n \t
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\r\n \t
- Regulation of gene expression\u00a0is extremely important during an organism's early development. [pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary] \u2014 which encode for chains of\u00a0amino acids\u00a0called [pb_glossary id=\"2413\"]homeodomains[\/pb_glossary] \u2014 are important genes that regulate development.<\/li>\r\n \t
- Some types of [pb_glossary id=\"5605\"]cancer[\/pb_glossary] occur because of\u00a0[pb_glossary id=\"2381\"]mutations[\/pb_glossary]\u00a0in the genes that control the\u00a0[pb_glossary id=\"5643\"]cell cycle[\/pb_glossary]. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Define gene expression.<\/li>\r\n \t
- Why must gene expression be regulated?<\/li>\r\n \t
- Explain how regulatory proteins may activate or repress transcription.<\/li>\r\n \t
- [h5p id=\"503\"]<\/li>\r\n \t
- What is the TATA box, and how does it work?<\/li>\r\n \t
- Describe homeobox genes and their role in\u00a0an organism's development.<\/li>\r\n \t
- Discuss the role of regulatory gene mutations in cancer.<\/li>\r\n \t
- Explain the relationship between proto-oncogenes and oncogenes.<\/li>\r\n \t
- If a newly fertilized egg contained a\u00a0mutation\u00a0in a homeobox gene,\u00a0how do you think this would affect the developing embryo? Explain your answer.<\/li>\r\n \t
- Compare and contrast enhancers and activators.<\/li>\r\n<\/ol>\r\n \r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Explore More<\/strong><\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?time_continue=3&v=vi-zWoobt_Q&feature=emb_logo\r\nRegulated Transcription, ndsuvirtualcell, 2008.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan,\r\nTED-Ed, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE\r\n
What is leukemia? - Danilo Allegra and Dania Puggioni, 2015.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 5.9.1<\/strong>\r\n\r\nStem_cell_differentiation.svg<\/a> by Haileyfournier<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.2<\/strong>\r\n\r\nActivators and Repressors by Christine Miller is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.3<\/strong>\r\n\r\nTATA_box_description<\/a> by Luttysar<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.4<\/strong>\r\n\r\nPathways to cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\r\n\r\n \r\n\r\nReferences<\/span>\r\nBrainard, J\/ CK-12 Foundation. (2012). Figure 3 Flow chart (series of mutations leading to cancer) [digital image]. In CK-12 College Human Biology <\/em>(Section 5.8) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/c\/physical-science\/concentration\/?referrer=crossref<\/span><\/p>\r\nndsuvirtualcell.(2008). Regulated transcription. YouTube. https:\/\/www.youtube.com\/watch?v=vi-zWoobt_Q&feature=youtu.be<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, April 15). What is leukemia? - Danilo Allegra and Dania Puggioni. YouTube. https:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE&feature=youtu.be<\/p>","rendered":"
<\/p>\nFigure 5.9.1 Differentiation pathways for a stem cell based on gene regulation. <\/em><\/figcaption><\/figure>\n\nExpress Yourself<\/h1>\n<\/div>\n
This sketch illustrates some of the variability in human\u00a0cells<\/a>. The shape and other\u00a0characteristics\u00a0that make each type of cell unique depend mainly on the\u00a0specific\u00a0proteins\u00a0that particular cell type makes. Proteins are encoded in genes. All the\u00a0cells\u00a0in an organism have the same genes, so they all have genetic instructions for the same proteins. Obviously, different types of cells must use (or express) different genes to make different proteins.<\/p>\n\nWhat Is Gene Expression?<\/h1>\n<\/div>\n
Using a gene<\/a> to make a\u00a0protein<\/a>\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of transcription<\/a> of DNA<\/a> into mRNA<\/a>,\u00a0 and translation<\/a> of mRNA into a protein. It may also include further processing of the protein after synthesis.<\/p>\nGene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in eukaryotic<\/a>\u00a0cells, and it is the focus of this concept.<\/p>\n\nRegulation of Transcription<\/h1>\n<\/div>\nFigure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em><\/figcaption><\/figure>\nAs shown in Figure 5.9.2, transcription is controlled by regulatory proteins<\/a><\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0regulatory elements<\/a><\/strong>, which are located near promoters. The promoter<\/a> is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to mRNA<\/a>. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0Activators<\/a><\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0Repressors<\/a><\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.<\/p>\n <\/p>\n
\nEnhancers<\/span><\/p>\n<\/div>\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene’s promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.Enhancers<\/a><\/p>\nThe TATA Box<\/h2>\n
Different types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0TATA box<\/a><\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.<\/p>\nFigure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em><\/figcaption><\/figure>\n\nRegulation During\u00a0Development<\/h1>\n<\/div>\n
The\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism’s early\u00a0development. Regulatory proteins must “turn on” certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.<\/p>\n
Homeobox genes<\/a><\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0embryonic<\/a> stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0amino acids<\/a>, called\u00a0homeodomains<\/a><\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.<\/p>\n\nGene Expression and\u00a0Cancer<\/h1>\n<\/div>\nFigure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em><\/figcaption><\/figure>\nSome types of cancer <\/a>occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.<\/p>\n\n- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car’s accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can’t be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n<\/ul>\n
<\/p>\n
<\/p>\n
\n\n\n5.9 Summary<\/span><\/h1>\n<\/header>\n\n\n- Using a gene<\/a> to make a protein<\/a> is called gene expression<\/a>. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0protein synthesis<\/a>\u00a0or processing.<\/li>\n
- The regulation of transcription<\/a> is controlled by regulatory proteins <\/a>that bind to regions of DNA called regulatory elements<\/a>, which are usually located near promoters<\/a>. Most regulatory proteins are either activators<\/a> that promote transcription, or repressors<\/a> that impede transcription.<\/li>\n
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\n
- Regulation of gene expression\u00a0is extremely important during an organism’s early development. Homeobox genes<\/a> \u2014 which encode for chains of\u00a0amino acids\u00a0called homeodomains<\/a> \u2014 are important genes that regulate development.<\/li>\n
- Some types of cancer<\/a> occur because of\u00a0mutations<\/a>\u00a0in the genes that control the\u00a0cell cycle<\/a>. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.9 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define gene expression.<\/li>\n
- Why must gene expression be regulated?<\/li>\n
- Explain how regulatory proteins may activate or repress transcription.<\/li>\n
- \n\n
Regulation of Transcription<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_2407\" align=\"alignright\" width=\"718\"] Figure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em>[\/caption]\r\n\r\nAs shown in Figure 5.9.2, transcription is controlled by [pb_glossary id=\"2402\"]regulatory proteins[\/pb_glossary]<\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0[pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary]<\/strong>, which are located near promoters. The [pb_glossary id=\"2404\"]promoter[\/pb_glossary] is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to [pb_glossary id=\"2212\"]mRNA[\/pb_glossary]. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0[pb_glossary id=\"2405\"]Activators[\/pb_glossary]<\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0[pb_glossary id=\"2406\"]Repressors[\/pb_glossary]<\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.\r\n\r\n \r\n\r\n\r\nEnhancers<\/span>\r\n\r\n<\/div>\r\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene's promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.[pb_glossary id=\"2409\"]Enhancers[\/pb_glossary]\r\nThe TATA Box<\/h2>\r\nDifferent types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0[pb_glossary id=\"2410\"]TATA box[\/pb_glossary]<\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.\r\n\r\n[caption id=\"attachment_2450\" align=\"aligncenter\" width=\"886\"] Figure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em>[\/caption]\r\n\r\n\r\nRegulation During\u00a0Development<\/h1>\r\n<\/div>\r\nThe\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism's early\u00a0development. Regulatory proteins must \"turn on\" certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.\r\n\r\n[pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary]<\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0[pb_glossary id=\"5983\"]embryonic[\/pb_glossary] stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0[pb_glossary id=\"5707\"]amino acids[\/pb_glossary], called\u00a0[pb_glossary id=\"2413\"]homeodomains[\/pb_glossary]<\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.\r\n\r\nGene Expression and\u00a0Cancer<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_2416\" align=\"alignleft\" width=\"315\"] Figure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em>[\/caption]\r\n\r\nSome types of [pb_glossary id=\"5605\"]cancer [\/pb_glossary]occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.\r\n\r\n \t- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car's accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n \t
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can't be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n<\/ul>\r\n \r\n\r\n \r\n\r\n
\r\n5.9 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Using a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a [pb_glossary id=\"5813\"]protein[\/pb_glossary] is called [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0[pb_glossary id=\"2210\"]protein synthesis[\/pb_glossary]\u00a0or processing.<\/li>\r\n \t
- The regulation of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] is controlled by [pb_glossary id=\"2402\"]regulatory proteins [\/pb_glossary]that bind to regions of DNA called [pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary], which are usually located near [pb_glossary id=\"2404\"]promoters[\/pb_glossary]. Most regulatory proteins are either [pb_glossary id=\"2405\"]activators[\/pb_glossary] that promote transcription, or [pb_glossary id=\"2406\"]repressors[\/pb_glossary] that impede transcription.<\/li>\r\n \t
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\r\n \t
- Regulation of gene expression\u00a0is extremely important during an organism's early development. [pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary] \u2014 which encode for chains of\u00a0amino acids\u00a0called [pb_glossary id=\"2413\"]homeodomains[\/pb_glossary] \u2014 are important genes that regulate development.<\/li>\r\n \t
- Some types of [pb_glossary id=\"5605\"]cancer[\/pb_glossary] occur because of\u00a0[pb_glossary id=\"2381\"]mutations[\/pb_glossary]\u00a0in the genes that control the\u00a0[pb_glossary id=\"5643\"]cell cycle[\/pb_glossary]. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Define gene expression.<\/li>\r\n \t
- Why must gene expression be regulated?<\/li>\r\n \t
- Explain how regulatory proteins may activate or repress transcription.<\/li>\r\n \t
- [h5p id=\"503\"]<\/li>\r\n \t
- What is the TATA box, and how does it work?<\/li>\r\n \t
- Describe homeobox genes and their role in\u00a0an organism's development.<\/li>\r\n \t
- Discuss the role of regulatory gene mutations in cancer.<\/li>\r\n \t
- Explain the relationship between proto-oncogenes and oncogenes.<\/li>\r\n \t
- If a newly fertilized egg contained a\u00a0mutation\u00a0in a homeobox gene,\u00a0how do you think this would affect the developing embryo? Explain your answer.<\/li>\r\n \t
- Compare and contrast enhancers and activators.<\/li>\r\n<\/ol>\r\n \r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Explore More<\/strong><\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?time_continue=3&v=vi-zWoobt_Q&feature=emb_logo\r\nRegulated Transcription, ndsuvirtualcell, 2008.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan,\r\nTED-Ed, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE\r\n
What is leukemia? - Danilo Allegra and Dania Puggioni, 2015.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 5.9.1<\/strong>\r\n\r\nStem_cell_differentiation.svg<\/a> by Haileyfournier<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.2<\/strong>\r\n\r\nActivators and Repressors by Christine Miller is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.3<\/strong>\r\n\r\nTATA_box_description<\/a> by Luttysar<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.4<\/strong>\r\n\r\nPathways to cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\r\n\r\n \r\n\r\nReferences<\/span>\r\nBrainard, J\/ CK-12 Foundation. (2012). Figure 3 Flow chart (series of mutations leading to cancer) [digital image]. In CK-12 College Human Biology <\/em>(Section 5.8) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/c\/physical-science\/concentration\/?referrer=crossref<\/span><\/p>\r\nndsuvirtualcell.(2008). Regulated transcription. YouTube. https:\/\/www.youtube.com\/watch?v=vi-zWoobt_Q&feature=youtu.be<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, April 15). What is leukemia? - Danilo Allegra and Dania Puggioni. YouTube. https:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE&feature=youtu.be<\/p>","rendered":"
<\/p>\nFigure 5.9.1 Differentiation pathways for a stem cell based on gene regulation. <\/em><\/figcaption><\/figure>\n\nExpress Yourself<\/h1>\n<\/div>\n
This sketch illustrates some of the variability in human\u00a0cells<\/a>. The shape and other\u00a0characteristics\u00a0that make each type of cell unique depend mainly on the\u00a0specific\u00a0proteins\u00a0that particular cell type makes. Proteins are encoded in genes. All the\u00a0cells\u00a0in an organism have the same genes, so they all have genetic instructions for the same proteins. Obviously, different types of cells must use (or express) different genes to make different proteins.<\/p>\n\nWhat Is Gene Expression?<\/h1>\n<\/div>\n
Using a gene<\/a> to make a\u00a0protein<\/a>\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of transcription<\/a> of DNA<\/a> into mRNA<\/a>,\u00a0 and translation<\/a> of mRNA into a protein. It may also include further processing of the protein after synthesis.<\/p>\nGene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in eukaryotic<\/a>\u00a0cells, and it is the focus of this concept.<\/p>\n\nRegulation of Transcription<\/h1>\n<\/div>\nFigure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em><\/figcaption><\/figure>\nAs shown in Figure 5.9.2, transcription is controlled by regulatory proteins<\/a><\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0regulatory elements<\/a><\/strong>, which are located near promoters. The promoter<\/a> is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to mRNA<\/a>. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0Activators<\/a><\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0Repressors<\/a><\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.<\/p>\n <\/p>\n
\nEnhancers<\/span><\/p>\n<\/div>\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene’s promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.Enhancers<\/a><\/p>\nThe TATA Box<\/h2>\n
Different types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0TATA box<\/a><\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.<\/p>\nFigure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em><\/figcaption><\/figure>\n\nRegulation During\u00a0Development<\/h1>\n<\/div>\n
The\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism’s early\u00a0development. Regulatory proteins must “turn on” certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.<\/p>\n
Homeobox genes<\/a><\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0embryonic<\/a> stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0amino acids<\/a>, called\u00a0homeodomains<\/a><\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.<\/p>\n\nGene Expression and\u00a0Cancer<\/h1>\n<\/div>\nFigure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em><\/figcaption><\/figure>\nSome types of cancer <\/a>occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.<\/p>\n\n- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car’s accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can’t be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n<\/ul>\n
<\/p>\n
<\/p>\n
\n\n\n5.9 Summary<\/span><\/h1>\n<\/header>\n\n\n- Using a gene<\/a> to make a protein<\/a> is called gene expression<\/a>. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0protein synthesis<\/a>\u00a0or processing.<\/li>\n
- The regulation of transcription<\/a> is controlled by regulatory proteins <\/a>that bind to regions of DNA called regulatory elements<\/a>, which are usually located near promoters<\/a>. Most regulatory proteins are either activators<\/a> that promote transcription, or repressors<\/a> that impede transcription.<\/li>\n
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\n
- Regulation of gene expression\u00a0is extremely important during an organism’s early development. Homeobox genes<\/a> \u2014 which encode for chains of\u00a0amino acids\u00a0called homeodomains<\/a> \u2014 are important genes that regulate development.<\/li>\n
- Some types of cancer<\/a> occur because of\u00a0mutations<\/a>\u00a0in the genes that control the\u00a0cell cycle<\/a>. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.9 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define gene expression.<\/li>\n
- Why must gene expression be regulated?<\/li>\n
- Explain how regulatory proteins may activate or repress transcription.<\/li>\n
- \n\n
The TATA Box<\/h2>\r\nDifferent types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0[pb_glossary id=\"2410\"]TATA box[\/pb_glossary]<\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.\r\n\r\n[caption id=\"attachment_2450\" align=\"aligncenter\" width=\"886\"] Figure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em>[\/caption]\r\n\r\n\r\nRegulation During\u00a0Development<\/h1>\r\n<\/div>\r\nThe\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism's early\u00a0development. Regulatory proteins must \"turn on\" certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.\r\n\r\n[pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary]<\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0[pb_glossary id=\"5983\"]embryonic[\/pb_glossary] stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0[pb_glossary id=\"5707\"]amino acids[\/pb_glossary], called\u00a0[pb_glossary id=\"2413\"]homeodomains[\/pb_glossary]<\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.\r\n\r\nGene Expression and\u00a0Cancer<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_2416\" align=\"alignleft\" width=\"315\"] Figure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em>[\/caption]\r\n\r\nSome types of [pb_glossary id=\"5605\"]cancer [\/pb_glossary]occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.\r\n\r\n \t- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car's accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n \t
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can't be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n<\/ul>\r\n \r\n\r\n \r\n\r\n
\r\n5.9 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Using a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a [pb_glossary id=\"5813\"]protein[\/pb_glossary] is called [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0[pb_glossary id=\"2210\"]protein synthesis[\/pb_glossary]\u00a0or processing.<\/li>\r\n \t
- The regulation of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] is controlled by [pb_glossary id=\"2402\"]regulatory proteins [\/pb_glossary]that bind to regions of DNA called [pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary], which are usually located near [pb_glossary id=\"2404\"]promoters[\/pb_glossary]. Most regulatory proteins are either [pb_glossary id=\"2405\"]activators[\/pb_glossary] that promote transcription, or [pb_glossary id=\"2406\"]repressors[\/pb_glossary] that impede transcription.<\/li>\r\n \t
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\r\n \t
- Regulation of gene expression\u00a0is extremely important during an organism's early development. [pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary] \u2014 which encode for chains of\u00a0amino acids\u00a0called [pb_glossary id=\"2413\"]homeodomains[\/pb_glossary] \u2014 are important genes that regulate development.<\/li>\r\n \t
- Some types of [pb_glossary id=\"5605\"]cancer[\/pb_glossary] occur because of\u00a0[pb_glossary id=\"2381\"]mutations[\/pb_glossary]\u00a0in the genes that control the\u00a0[pb_glossary id=\"5643\"]cell cycle[\/pb_glossary]. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Define gene expression.<\/li>\r\n \t
- Why must gene expression be regulated?<\/li>\r\n \t
- Explain how regulatory proteins may activate or repress transcription.<\/li>\r\n \t
- [h5p id=\"503\"]<\/li>\r\n \t
- What is the TATA box, and how does it work?<\/li>\r\n \t
- Describe homeobox genes and their role in\u00a0an organism's development.<\/li>\r\n \t
- Discuss the role of regulatory gene mutations in cancer.<\/li>\r\n \t
- Explain the relationship between proto-oncogenes and oncogenes.<\/li>\r\n \t
- If a newly fertilized egg contained a\u00a0mutation\u00a0in a homeobox gene,\u00a0how do you think this would affect the developing embryo? Explain your answer.<\/li>\r\n \t
- Compare and contrast enhancers and activators.<\/li>\r\n<\/ol>\r\n \r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Explore More<\/strong><\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?time_continue=3&v=vi-zWoobt_Q&feature=emb_logo\r\nRegulated Transcription, ndsuvirtualcell, 2008.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan,\r\nTED-Ed, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE\r\n
What is leukemia? - Danilo Allegra and Dania Puggioni, 2015.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 5.9.1<\/strong>\r\n\r\nStem_cell_differentiation.svg<\/a> by Haileyfournier<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.2<\/strong>\r\n\r\nActivators and Repressors by Christine Miller is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.3<\/strong>\r\n\r\nTATA_box_description<\/a> by Luttysar<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.4<\/strong>\r\n\r\nPathways to cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\r\n\r\n \r\n\r\nReferences<\/span>\r\nBrainard, J\/ CK-12 Foundation. (2012). Figure 3 Flow chart (series of mutations leading to cancer) [digital image]. In CK-12 College Human Biology <\/em>(Section 5.8) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/c\/physical-science\/concentration\/?referrer=crossref<\/span><\/p>\r\nndsuvirtualcell.(2008). Regulated transcription. YouTube. https:\/\/www.youtube.com\/watch?v=vi-zWoobt_Q&feature=youtu.be<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, April 15). What is leukemia? - Danilo Allegra and Dania Puggioni. YouTube. https:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE&feature=youtu.be<\/p>","rendered":"
<\/p>\nFigure 5.9.1 Differentiation pathways for a stem cell based on gene regulation. <\/em><\/figcaption><\/figure>\n\nExpress Yourself<\/h1>\n<\/div>\n
This sketch illustrates some of the variability in human\u00a0cells<\/a>. The shape and other\u00a0characteristics\u00a0that make each type of cell unique depend mainly on the\u00a0specific\u00a0proteins\u00a0that particular cell type makes. Proteins are encoded in genes. All the\u00a0cells\u00a0in an organism have the same genes, so they all have genetic instructions for the same proteins. Obviously, different types of cells must use (or express) different genes to make different proteins.<\/p>\n\nWhat Is Gene Expression?<\/h1>\n<\/div>\n
Using a gene<\/a> to make a\u00a0protein<\/a>\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of transcription<\/a> of DNA<\/a> into mRNA<\/a>,\u00a0 and translation<\/a> of mRNA into a protein. It may also include further processing of the protein after synthesis.<\/p>\nGene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in eukaryotic<\/a>\u00a0cells, and it is the focus of this concept.<\/p>\n\nRegulation of Transcription<\/h1>\n<\/div>\nFigure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em><\/figcaption><\/figure>\nAs shown in Figure 5.9.2, transcription is controlled by regulatory proteins<\/a><\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0regulatory elements<\/a><\/strong>, which are located near promoters. The promoter<\/a> is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to mRNA<\/a>. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0Activators<\/a><\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0Repressors<\/a><\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.<\/p>\n <\/p>\n
\nEnhancers<\/span><\/p>\n<\/div>\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene’s promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.Enhancers<\/a><\/p>\nThe TATA Box<\/h2>\n
Different types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0TATA box<\/a><\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.<\/p>\nFigure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em><\/figcaption><\/figure>\n\nRegulation During\u00a0Development<\/h1>\n<\/div>\n
The\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism’s early\u00a0development. Regulatory proteins must “turn on” certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.<\/p>\n
Homeobox genes<\/a><\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0embryonic<\/a> stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0amino acids<\/a>, called\u00a0homeodomains<\/a><\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.<\/p>\n\nGene Expression and\u00a0Cancer<\/h1>\n<\/div>\nFigure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em><\/figcaption><\/figure>\nSome types of cancer <\/a>occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.<\/p>\n\n- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car’s accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can’t be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n<\/ul>\n
<\/p>\n
<\/p>\n
\n\n\n5.9 Summary<\/span><\/h1>\n<\/header>\n\n\n- Using a gene<\/a> to make a protein<\/a> is called gene expression<\/a>. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0protein synthesis<\/a>\u00a0or processing.<\/li>\n
- The regulation of transcription<\/a> is controlled by regulatory proteins <\/a>that bind to regions of DNA called regulatory elements<\/a>, which are usually located near promoters<\/a>. Most regulatory proteins are either activators<\/a> that promote transcription, or repressors<\/a> that impede transcription.<\/li>\n
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\n
- Regulation of gene expression\u00a0is extremely important during an organism’s early development. Homeobox genes<\/a> \u2014 which encode for chains of\u00a0amino acids\u00a0called homeodomains<\/a> \u2014 are important genes that regulate development.<\/li>\n
- Some types of cancer<\/a> occur because of\u00a0mutations<\/a>\u00a0in the genes that control the\u00a0cell cycle<\/a>. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.9 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define gene expression.<\/li>\n
- Why must gene expression be regulated?<\/li>\n
- Explain how regulatory proteins may activate or repress transcription.<\/li>\n
- \n\n
Regulation During\u00a0Development<\/h1>\r\n<\/div>\r\nThe\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism's early\u00a0development. Regulatory proteins must \"turn on\" certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.\r\n\r\n[pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary]<\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0[pb_glossary id=\"5983\"]embryonic[\/pb_glossary] stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0[pb_glossary id=\"5707\"]amino acids[\/pb_glossary], called\u00a0[pb_glossary id=\"2413\"]homeodomains[\/pb_glossary]<\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.\r\n\r\nGene Expression and\u00a0Cancer<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_2416\" align=\"alignleft\" width=\"315\"] Figure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em>[\/caption]\r\n\r\nSome types of [pb_glossary id=\"5605\"]cancer [\/pb_glossary]occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.\r\n\r\n \t- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car's accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n \t
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can't be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n<\/ul>\r\n \r\n\r\n \r\n\r\n
\r\n5.9 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Using a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a [pb_glossary id=\"5813\"]protein[\/pb_glossary] is called [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0[pb_glossary id=\"2210\"]protein synthesis[\/pb_glossary]\u00a0or processing.<\/li>\r\n \t
- The regulation of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] is controlled by [pb_glossary id=\"2402\"]regulatory proteins [\/pb_glossary]that bind to regions of DNA called [pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary], which are usually located near [pb_glossary id=\"2404\"]promoters[\/pb_glossary]. Most regulatory proteins are either [pb_glossary id=\"2405\"]activators[\/pb_glossary] that promote transcription, or [pb_glossary id=\"2406\"]repressors[\/pb_glossary] that impede transcription.<\/li>\r\n \t
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\r\n \t
- Regulation of gene expression\u00a0is extremely important during an organism's early development. [pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary] \u2014 which encode for chains of\u00a0amino acids\u00a0called [pb_glossary id=\"2413\"]homeodomains[\/pb_glossary] \u2014 are important genes that regulate development.<\/li>\r\n \t
- Some types of [pb_glossary id=\"5605\"]cancer[\/pb_glossary] occur because of\u00a0[pb_glossary id=\"2381\"]mutations[\/pb_glossary]\u00a0in the genes that control the\u00a0[pb_glossary id=\"5643\"]cell cycle[\/pb_glossary]. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Define gene expression.<\/li>\r\n \t
- Why must gene expression be regulated?<\/li>\r\n \t
- Explain how regulatory proteins may activate or repress transcription.<\/li>\r\n \t
- [h5p id=\"503\"]<\/li>\r\n \t
- What is the TATA box, and how does it work?<\/li>\r\n \t
- Describe homeobox genes and their role in\u00a0an organism's development.<\/li>\r\n \t
- Discuss the role of regulatory gene mutations in cancer.<\/li>\r\n \t
- Explain the relationship between proto-oncogenes and oncogenes.<\/li>\r\n \t
- If a newly fertilized egg contained a\u00a0mutation\u00a0in a homeobox gene,\u00a0how do you think this would affect the developing embryo? Explain your answer.<\/li>\r\n \t
- Compare and contrast enhancers and activators.<\/li>\r\n<\/ol>\r\n \r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Explore More<\/strong><\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?time_continue=3&v=vi-zWoobt_Q&feature=emb_logo\r\nRegulated Transcription, ndsuvirtualcell, 2008.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan,\r\nTED-Ed, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE\r\n
What is leukemia? - Danilo Allegra and Dania Puggioni, 2015.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 5.9.1<\/strong>\r\n\r\nStem_cell_differentiation.svg<\/a> by Haileyfournier<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.2<\/strong>\r\n\r\nActivators and Repressors by Christine Miller is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.3<\/strong>\r\n\r\nTATA_box_description<\/a> by Luttysar<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.4<\/strong>\r\n\r\nPathways to cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\r\n\r\n \r\n\r\nReferences<\/span>\r\nBrainard, J\/ CK-12 Foundation. (2012). Figure 3 Flow chart (series of mutations leading to cancer) [digital image]. In CK-12 College Human Biology <\/em>(Section 5.8) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/c\/physical-science\/concentration\/?referrer=crossref<\/span><\/p>\r\nndsuvirtualcell.(2008). Regulated transcription. YouTube. https:\/\/www.youtube.com\/watch?v=vi-zWoobt_Q&feature=youtu.be<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, April 15). What is leukemia? - Danilo Allegra and Dania Puggioni. YouTube. https:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE&feature=youtu.be<\/p>","rendered":"
<\/p>\nFigure 5.9.1 Differentiation pathways for a stem cell based on gene regulation. <\/em><\/figcaption><\/figure>\n\nExpress Yourself<\/h1>\n<\/div>\n
This sketch illustrates some of the variability in human\u00a0cells<\/a>. The shape and other\u00a0characteristics\u00a0that make each type of cell unique depend mainly on the\u00a0specific\u00a0proteins\u00a0that particular cell type makes. Proteins are encoded in genes. All the\u00a0cells\u00a0in an organism have the same genes, so they all have genetic instructions for the same proteins. Obviously, different types of cells must use (or express) different genes to make different proteins.<\/p>\n\nWhat Is Gene Expression?<\/h1>\n<\/div>\n
Using a gene<\/a> to make a\u00a0protein<\/a>\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of transcription<\/a> of DNA<\/a> into mRNA<\/a>,\u00a0 and translation<\/a> of mRNA into a protein. It may also include further processing of the protein after synthesis.<\/p>\nGene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in eukaryotic<\/a>\u00a0cells, and it is the focus of this concept.<\/p>\n\nRegulation of Transcription<\/h1>\n<\/div>\nFigure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em><\/figcaption><\/figure>\nAs shown in Figure 5.9.2, transcription is controlled by regulatory proteins<\/a><\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0regulatory elements<\/a><\/strong>, which are located near promoters. The promoter<\/a> is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to mRNA<\/a>. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0Activators<\/a><\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0Repressors<\/a><\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.<\/p>\n <\/p>\n
\nEnhancers<\/span><\/p>\n<\/div>\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene’s promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.Enhancers<\/a><\/p>\nThe TATA Box<\/h2>\n
Different types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0TATA box<\/a><\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.<\/p>\nFigure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em><\/figcaption><\/figure>\n\nRegulation During\u00a0Development<\/h1>\n<\/div>\n
The\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism’s early\u00a0development. Regulatory proteins must “turn on” certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.<\/p>\n
Homeobox genes<\/a><\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0embryonic<\/a> stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0amino acids<\/a>, called\u00a0homeodomains<\/a><\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.<\/p>\n\nGene Expression and\u00a0Cancer<\/h1>\n<\/div>\nFigure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em><\/figcaption><\/figure>\nSome types of cancer <\/a>occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.<\/p>\n\n- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car’s accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can’t be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n<\/ul>\n
<\/p>\n
<\/p>\n
\n\n\n5.9 Summary<\/span><\/h1>\n<\/header>\n\n\n- Using a gene<\/a> to make a protein<\/a> is called gene expression<\/a>. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0protein synthesis<\/a>\u00a0or processing.<\/li>\n
- The regulation of transcription<\/a> is controlled by regulatory proteins <\/a>that bind to regions of DNA called regulatory elements<\/a>, which are usually located near promoters<\/a>. Most regulatory proteins are either activators<\/a> that promote transcription, or repressors<\/a> that impede transcription.<\/li>\n
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\n
- Regulation of gene expression\u00a0is extremely important during an organism’s early development. Homeobox genes<\/a> \u2014 which encode for chains of\u00a0amino acids\u00a0called homeodomains<\/a> \u2014 are important genes that regulate development.<\/li>\n
- Some types of cancer<\/a> occur because of\u00a0mutations<\/a>\u00a0in the genes that control the\u00a0cell cycle<\/a>. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.9 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define gene expression.<\/li>\n
- Why must gene expression be regulated?<\/li>\n
- Explain how regulatory proteins may activate or repress transcription.<\/li>\n
- \n\n
Gene Expression and\u00a0Cancer<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_2416\" align=\"alignleft\" width=\"315\"] Figure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em>[\/caption]\r\n\r\nSome types of [pb_glossary id=\"5605\"]cancer [\/pb_glossary]occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.\r\n\r\n \t- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car's accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n \t
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can't be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\r\n<\/ul>\r\n \r\n\r\n \r\n\r\n
\r\n5.9 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Using a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a [pb_glossary id=\"5813\"]protein[\/pb_glossary] is called [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0[pb_glossary id=\"2210\"]protein synthesis[\/pb_glossary]\u00a0or processing.<\/li>\r\n \t
- The regulation of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] is controlled by [pb_glossary id=\"2402\"]regulatory proteins [\/pb_glossary]that bind to regions of DNA called [pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary], which are usually located near [pb_glossary id=\"2404\"]promoters[\/pb_glossary]. Most regulatory proteins are either [pb_glossary id=\"2405\"]activators[\/pb_glossary] that promote transcription, or [pb_glossary id=\"2406\"]repressors[\/pb_glossary] that impede transcription.<\/li>\r\n \t
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\r\n \t
- Regulation of gene expression\u00a0is extremely important during an organism's early development. [pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary] \u2014 which encode for chains of\u00a0amino acids\u00a0called [pb_glossary id=\"2413\"]homeodomains[\/pb_glossary] \u2014 are important genes that regulate development.<\/li>\r\n \t
- Some types of [pb_glossary id=\"5605\"]cancer[\/pb_glossary] occur because of\u00a0[pb_glossary id=\"2381\"]mutations[\/pb_glossary]\u00a0in the genes that control the\u00a0[pb_glossary id=\"5643\"]cell cycle[\/pb_glossary]. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Define gene expression.<\/li>\r\n \t
- Why must gene expression be regulated?<\/li>\r\n \t
- Explain how regulatory proteins may activate or repress transcription.<\/li>\r\n \t
- [h5p id=\"503\"]<\/li>\r\n \t
- What is the TATA box, and how does it work?<\/li>\r\n \t
- Describe homeobox genes and their role in\u00a0an organism's development.<\/li>\r\n \t
- Discuss the role of regulatory gene mutations in cancer.<\/li>\r\n \t
- Explain the relationship between proto-oncogenes and oncogenes.<\/li>\r\n \t
- If a newly fertilized egg contained a\u00a0mutation\u00a0in a homeobox gene,\u00a0how do you think this would affect the developing embryo? Explain your answer.<\/li>\r\n \t
- Compare and contrast enhancers and activators.<\/li>\r\n<\/ol>\r\n \r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Explore More<\/strong><\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?time_continue=3&v=vi-zWoobt_Q&feature=emb_logo\r\nRegulated Transcription, ndsuvirtualcell, 2008.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan,\r\nTED-Ed, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE\r\n
What is leukemia? - Danilo Allegra and Dania Puggioni, 2015.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 5.9.1<\/strong>\r\n\r\nStem_cell_differentiation.svg<\/a> by Haileyfournier<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.2<\/strong>\r\n\r\nActivators and Repressors by Christine Miller is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.3<\/strong>\r\n\r\nTATA_box_description<\/a> by Luttysar<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.4<\/strong>\r\n\r\nPathways to cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\r\n\r\n \r\n\r\nReferences<\/span>\r\nBrainard, J\/ CK-12 Foundation. (2012). Figure 3 Flow chart (series of mutations leading to cancer) [digital image]. In CK-12 College Human Biology <\/em>(Section 5.8) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/c\/physical-science\/concentration\/?referrer=crossref<\/span><\/p>\r\nndsuvirtualcell.(2008). Regulated transcription. YouTube. https:\/\/www.youtube.com\/watch?v=vi-zWoobt_Q&feature=youtu.be<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, April 15). What is leukemia? - Danilo Allegra and Dania Puggioni. YouTube. https:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE&feature=youtu.be<\/p>","rendered":"
<\/p>\nFigure 5.9.1 Differentiation pathways for a stem cell based on gene regulation. <\/em><\/figcaption><\/figure>\n\nExpress Yourself<\/h1>\n<\/div>\n
This sketch illustrates some of the variability in human\u00a0cells<\/a>. The shape and other\u00a0characteristics\u00a0that make each type of cell unique depend mainly on the\u00a0specific\u00a0proteins\u00a0that particular cell type makes. Proteins are encoded in genes. All the\u00a0cells\u00a0in an organism have the same genes, so they all have genetic instructions for the same proteins. Obviously, different types of cells must use (or express) different genes to make different proteins.<\/p>\n\nWhat Is Gene Expression?<\/h1>\n<\/div>\n
Using a gene<\/a> to make a\u00a0protein<\/a>\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of transcription<\/a> of DNA<\/a> into mRNA<\/a>,\u00a0 and translation<\/a> of mRNA into a protein. It may also include further processing of the protein after synthesis.<\/p>\nGene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in eukaryotic<\/a>\u00a0cells, and it is the focus of this concept.<\/p>\n\nRegulation of Transcription<\/h1>\n<\/div>\nFigure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em><\/figcaption><\/figure>\nAs shown in Figure 5.9.2, transcription is controlled by regulatory proteins<\/a><\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0regulatory elements<\/a><\/strong>, which are located near promoters. The promoter<\/a> is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to mRNA<\/a>. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0Activators<\/a><\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0Repressors<\/a><\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.<\/p>\n <\/p>\n
\nEnhancers<\/span><\/p>\n<\/div>\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene’s promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.Enhancers<\/a><\/p>\nThe TATA Box<\/h2>\n
Different types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0TATA box<\/a><\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.<\/p>\nFigure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em><\/figcaption><\/figure>\n\nRegulation During\u00a0Development<\/h1>\n<\/div>\n
The\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism’s early\u00a0development. Regulatory proteins must “turn on” certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.<\/p>\n
Homeobox genes<\/a><\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0embryonic<\/a> stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0amino acids<\/a>, called\u00a0homeodomains<\/a><\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.<\/p>\n\nGene Expression and\u00a0Cancer<\/h1>\n<\/div>\nFigure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em><\/figcaption><\/figure>\nSome types of cancer <\/a>occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.<\/p>\n\n- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car’s accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can’t be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n<\/ul>\n
<\/p>\n
<\/p>\n
\n\n\n5.9 Summary<\/span><\/h1>\n<\/header>\n\n\n- Using a gene<\/a> to make a protein<\/a> is called gene expression<\/a>. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0protein synthesis<\/a>\u00a0or processing.<\/li>\n
- The regulation of transcription<\/a> is controlled by regulatory proteins <\/a>that bind to regions of DNA called regulatory elements<\/a>, which are usually located near promoters<\/a>. Most regulatory proteins are either activators<\/a> that promote transcription, or repressors<\/a> that impede transcription.<\/li>\n
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\n
- Regulation of gene expression\u00a0is extremely important during an organism’s early development. Homeobox genes<\/a> \u2014 which encode for chains of\u00a0amino acids\u00a0called homeodomains<\/a> \u2014 are important genes that regulate development.<\/li>\n
- Some types of cancer<\/a> occur because of\u00a0mutations<\/a>\u00a0in the genes that control the\u00a0cell cycle<\/a>. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.9 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define gene expression.<\/li>\n
- Why must gene expression be regulated?<\/li>\n
- Explain how regulatory proteins may activate or repress transcription.<\/li>\n
- \n\n
5.9 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Using a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a [pb_glossary id=\"5813\"]protein[\/pb_glossary] is called [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0[pb_glossary id=\"2210\"]protein synthesis[\/pb_glossary]\u00a0or processing.<\/li>\r\n \t
- The regulation of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] is controlled by [pb_glossary id=\"2402\"]regulatory proteins [\/pb_glossary]that bind to regions of DNA called [pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary], which are usually located near [pb_glossary id=\"2404\"]promoters[\/pb_glossary]. Most regulatory proteins are either [pb_glossary id=\"2405\"]activators[\/pb_glossary] that promote transcription, or [pb_glossary id=\"2406\"]repressors[\/pb_glossary] that impede transcription.<\/li>\r\n \t
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\r\n \t
- Regulation of gene expression\u00a0is extremely important during an organism's early development. [pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary] \u2014 which encode for chains of\u00a0amino acids\u00a0called [pb_glossary id=\"2413\"]homeodomains[\/pb_glossary] \u2014 are important genes that regulate development.<\/li>\r\n \t
- Some types of [pb_glossary id=\"5605\"]cancer[\/pb_glossary] occur because of\u00a0[pb_glossary id=\"2381\"]mutations[\/pb_glossary]\u00a0in the genes that control the\u00a0[pb_glossary id=\"5643\"]cell cycle[\/pb_glossary]. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Define gene expression.<\/li>\r\n \t
- Why must gene expression be regulated?<\/li>\r\n \t
- Explain how regulatory proteins may activate or repress transcription.<\/li>\r\n \t
- [h5p id=\"503\"]<\/li>\r\n \t
- What is the TATA box, and how does it work?<\/li>\r\n \t
- Describe homeobox genes and their role in\u00a0an organism's development.<\/li>\r\n \t
- Discuss the role of regulatory gene mutations in cancer.<\/li>\r\n \t
- Explain the relationship between proto-oncogenes and oncogenes.<\/li>\r\n \t
- If a newly fertilized egg contained a\u00a0mutation\u00a0in a homeobox gene,\u00a0how do you think this would affect the developing embryo? Explain your answer.<\/li>\r\n \t
- Compare and contrast enhancers and activators.<\/li>\r\n<\/ol>\r\n \r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n5.9 Explore More<\/strong><\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?time_continue=3&v=vi-zWoobt_Q&feature=emb_logo\r\nRegulated Transcription, ndsuvirtualcell, 2008.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan,\r\nTED-Ed, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE\r\n
What is leukemia? - Danilo Allegra and Dania Puggioni, 2015.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 5.9.1<\/strong>\r\n\r\nStem_cell_differentiation.svg<\/a> by Haileyfournier<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.2<\/strong>\r\n\r\nActivators and Repressors by Christine Miller is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.3<\/strong>\r\n\r\nTATA_box_description<\/a> by Luttysar<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.4<\/strong>\r\n\r\nPathways to cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\r\n\r\n \r\n\r\nReferences<\/span>\r\nBrainard, J\/ CK-12 Foundation. (2012). Figure 3 Flow chart (series of mutations leading to cancer) [digital image]. In CK-12 College Human Biology <\/em>(Section 5.8) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/c\/physical-science\/concentration\/?referrer=crossref<\/span><\/p>\r\nndsuvirtualcell.(2008). Regulated transcription. YouTube. https:\/\/www.youtube.com\/watch?v=vi-zWoobt_Q&feature=youtu.be<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, April 15). What is leukemia? - Danilo Allegra and Dania Puggioni. YouTube. https:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE&feature=youtu.be<\/p>","rendered":"
<\/p>\nFigure 5.9.1 Differentiation pathways for a stem cell based on gene regulation. <\/em><\/figcaption><\/figure>\n\nExpress Yourself<\/h1>\n<\/div>\n
This sketch illustrates some of the variability in human\u00a0cells<\/a>. The shape and other\u00a0characteristics\u00a0that make each type of cell unique depend mainly on the\u00a0specific\u00a0proteins\u00a0that particular cell type makes. Proteins are encoded in genes. All the\u00a0cells\u00a0in an organism have the same genes, so they all have genetic instructions for the same proteins. Obviously, different types of cells must use (or express) different genes to make different proteins.<\/p>\n\nWhat Is Gene Expression?<\/h1>\n<\/div>\n
Using a gene<\/a> to make a\u00a0protein<\/a>\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of transcription<\/a> of DNA<\/a> into mRNA<\/a>,\u00a0 and translation<\/a> of mRNA into a protein. It may also include further processing of the protein after synthesis.<\/p>\nGene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in eukaryotic<\/a>\u00a0cells, and it is the focus of this concept.<\/p>\n\nRegulation of Transcription<\/h1>\n<\/div>\nFigure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em><\/figcaption><\/figure>\nAs shown in Figure 5.9.2, transcription is controlled by regulatory proteins<\/a><\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0regulatory elements<\/a><\/strong>, which are located near promoters. The promoter<\/a> is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to mRNA<\/a>. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0Activators<\/a><\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0Repressors<\/a><\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.<\/p>\n <\/p>\n
\nEnhancers<\/span><\/p>\n<\/div>\nAlthough regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene’s promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.Enhancers<\/a><\/p>\nThe TATA Box<\/h2>\n
Different types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0TATA box<\/a><\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.<\/p>\nFigure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em><\/figcaption><\/figure>\n\nRegulation During\u00a0Development<\/h1>\n<\/div>\n
The\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism’s early\u00a0development. Regulatory proteins must “turn on” certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.<\/p>\n
Homeobox genes<\/a><\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0embryonic<\/a> stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0amino acids<\/a>, called\u00a0homeodomains<\/a><\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.<\/p>\n\nGene Expression and\u00a0Cancer<\/h1>\n<\/div>\nFigure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em><\/figcaption><\/figure>\nSome types of cancer <\/a>occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.<\/p>\n\n- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car’s accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can’t be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n<\/ul>\n
<\/p>\n
<\/p>\n
\n\n\n5.9 Summary<\/span><\/h1>\n<\/header>\n\n\n- Using a gene<\/a> to make a protein<\/a> is called gene expression<\/a>. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0protein synthesis<\/a>\u00a0or processing.<\/li>\n
- The regulation of transcription<\/a> is controlled by regulatory proteins <\/a>that bind to regions of DNA called regulatory elements<\/a>, which are usually located near promoters<\/a>. Most regulatory proteins are either activators<\/a> that promote transcription, or repressors<\/a> that impede transcription.<\/li>\n
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\n
- Regulation of gene expression\u00a0is extremely important during an organism’s early development. Homeobox genes<\/a> \u2014 which encode for chains of\u00a0amino acids\u00a0called homeodomains<\/a> \u2014 are important genes that regulate development.<\/li>\n
- Some types of cancer<\/a> occur because of\u00a0mutations<\/a>\u00a0in the genes that control the\u00a0cell cycle<\/a>. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n5.9 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Define gene expression.<\/li>\n
- Why must gene expression be regulated?<\/li>\n
- Explain how regulatory proteins may activate or repress transcription.<\/li>\n
- \n\n
- \r\n \t
- Using a [pb_glossary id=\"5521\"]gene[\/pb_glossary] to make a [pb_glossary id=\"5813\"]protein[\/pb_glossary] is called [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0[pb_glossary id=\"2210\"]protein synthesis[\/pb_glossary]\u00a0or processing.<\/li>\r\n \t
- The regulation of [pb_glossary id=\"2241\"]transcription[\/pb_glossary] is controlled by [pb_glossary id=\"2402\"]regulatory proteins [\/pb_glossary]that bind to regions of DNA called [pb_glossary id=\"2403\"]regulatory elements[\/pb_glossary], which are usually located near [pb_glossary id=\"2404\"]promoters[\/pb_glossary]. Most regulatory proteins are either [pb_glossary id=\"2405\"]activators[\/pb_glossary] that promote transcription, or [pb_glossary id=\"2406\"]repressors[\/pb_glossary] that impede transcription.<\/li>\r\n \t
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\r\n \t
- Regulation of gene expression\u00a0is extremely important during an organism's early development. [pb_glossary id=\"2411\"]Homeobox genes[\/pb_glossary] \u2014 which encode for chains of\u00a0amino acids\u00a0called [pb_glossary id=\"2413\"]homeodomains[\/pb_glossary] \u2014 are important genes that regulate development.<\/li>\r\n \t
- Some types of [pb_glossary id=\"5605\"]cancer[\/pb_glossary] occur because of\u00a0[pb_glossary id=\"2381\"]mutations[\/pb_glossary]\u00a0in the genes that control the\u00a0[pb_glossary id=\"5643\"]cell cycle[\/pb_glossary]. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n 5.9 Review Questions<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- Define gene expression.<\/li>\r\n \t
- Why must gene expression be regulated?<\/li>\r\n \t
- Explain how regulatory proteins may activate or repress transcription.<\/li>\r\n \t
- [h5p id=\"503\"]<\/li>\r\n \t
- What is the TATA box, and how does it work?<\/li>\r\n \t
- Describe homeobox genes and their role in\u00a0an organism's development.<\/li>\r\n \t
- Discuss the role of regulatory gene mutations in cancer.<\/li>\r\n \t
- Explain the relationship between proto-oncogenes and oncogenes.<\/li>\r\n \t
- If a newly fertilized egg contained a\u00a0mutation\u00a0in a homeobox gene,\u00a0how do you think this would affect the developing embryo? Explain your answer.<\/li>\r\n \t
- Compare and contrast enhancers and activators.<\/li>\r\n<\/ol>\r\n \r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n 5.9 Explore More<\/strong><\/span><\/h1>\r\n<\/header>\r\n
\r\n\r\nhttps:\/\/www.youtube.com\/watch?time_continue=3&v=vi-zWoobt_Q&feature=emb_logo\r\nRegulated Transcription, ndsuvirtualcell, 2008.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan,\r\nTED-Ed, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE\r\n
What is leukemia? - Danilo Allegra and Dania Puggioni, 2015.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 5.9.1<\/strong>\r\n\r\nStem_cell_differentiation.svg<\/a> by Haileyfournier<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.2<\/strong>\r\n\r\nActivators and Repressors by Christine Miller is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.3<\/strong>\r\n\r\nTATA_box_description<\/a> by Luttysar<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 5.9.4<\/strong>\r\n\r\nPathways to cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n\r\n
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a>\r\n\r\n \r\n\r\nReferences<\/span>\r\nBrainard, J\/ CK-12 Foundation. (2012). Figure 3 Flow chart (series of mutations leading to cancer) [digital image]. In CK-12 College Human Biology <\/em>(Section 5.8) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/c\/physical-science\/concentration\/?referrer=crossref<\/span><\/p>\r\n
ndsuvirtualcell.(2008). Regulated transcription. YouTube. https:\/\/www.youtube.com\/watch?v=vi-zWoobt_Q&feature=youtu.be<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, April 15). What is leukemia? - Danilo Allegra and Dania Puggioni. YouTube. https:\/\/www.youtube.com\/watch?v=Z3B-AaqjyjE&feature=youtu.be<\/p>","rendered":"
<\/p>\n
Figure 5.9.1 Differentiation pathways for a stem cell based on gene regulation. <\/em><\/figcaption><\/figure>\n \nExpress Yourself<\/h1>\n<\/div>\n
This sketch illustrates some of the variability in human\u00a0cells<\/a>. The shape and other\u00a0characteristics\u00a0that make each type of cell unique depend mainly on the\u00a0specific\u00a0proteins\u00a0that particular cell type makes. Proteins are encoded in genes. All the\u00a0cells\u00a0in an organism have the same genes, so they all have genetic instructions for the same proteins. Obviously, different types of cells must use (or express) different genes to make different proteins.<\/p>\n
\nWhat Is Gene Expression?<\/h1>\n<\/div>\n
Using a gene<\/a> to make a\u00a0protein<\/a>\u00a0is called\u00a0gene expression<\/strong>. It includes the synthesis of the protein by the processes of transcription<\/a> of DNA<\/a> into mRNA<\/a>,\u00a0 and translation<\/a> of mRNA into a protein. It may also include further processing of the protein after synthesis.<\/p>\n
Gene expression is regulated to ensure that the correct\u00a0proteins\u00a0are made when and where they are needed. Regulation may occur at any point in the expression of a gene, from the start of the\u00a0transcription\u00a0phase of\u00a0protein synthesis\u00a0to the processing of a protein after synthesis occurs. The regulation of transcription is one of the most complicated parts of gene regulation in eukaryotic<\/a>\u00a0cells, and it is the focus of this concept.<\/p>\n
\nRegulation of Transcription<\/h1>\n<\/div>\n
Figure 5.9.2 Regulation of Transcription. Regulatory proteins bind to their corresponding regulatory elements in order to control transcription.<\/em><\/figcaption><\/figure>\n As shown in Figure 5.9.2, transcription is controlled by regulatory proteins<\/a><\/strong>. These proteins bind to regions of\u00a0DNA, called\u00a0regulatory elements<\/a><\/strong>, which are located near promoters. The promoter<\/a> is the region of a gene where\u00a0RNA\u00a0polymerase binds to initiate transcription of the\u00a0DNA to mRNA<\/a>. After regulatory proteins bind to regulatory elements, the proteins can interact with RNA polymerase. Regulatory proteins are typically either activators or repressors.\u00a0Activators<\/a><\/strong>\u00a0are regulatory proteins that promote transcription by enhancing the interaction of\u00a0RNA polymerase with the promoter.\u00a0Repressors<\/a><\/strong>\u00a0are regulatory proteins that prevent transcription by impeding the progress of\u00a0RNA\u00a0polymerase along the DNA strand, so the DNA cannot be transcribed to mRNA.<\/p>\n
<\/p>\n
\nEnhancers<\/span><\/p>\n<\/div>\n
Although regulatory proteins and elements are typically the key players in the regulation of transcription, other factors may also be involved.\u00a0Regulation of transcription may also involve enhancers.\u00a0Enhancers<\/strong>\u00a0are distant regions of DNA that can loop back to interact with a gene’s promoter. They can also\u00a0increase the likelihood that transcription of the gene will occur.Enhancers<\/a><\/p>\n
The TATA Box<\/h2>\n
Different types of cells have unique patterns of regulatory elements that result in\u00a0only<\/em>\u00a0the necessary genes being transcribed. That\u2019s why a\u00a0blood cell and nerve cell, for example, are so different from each other. Some regulatory elements, however, are common to virtually\u00a0all<\/em>\u00a0genes, regardless of the cells in which they occur. An example is the\u00a0TATA box<\/a><\/strong>, which\u00a0is a regulatory\u00a0element\u00a0that is part of the promoter of almost every eukaryotic gene. A number of regulatory proteins bind to the TATA box, forming a multi-protein complex. It is only when all of the appropriate proteins are bound to the TATA box that RNA polymerase recognizes the complex and binds to the promoter so transcription can begin.<\/p>\n
Figure 5.9.3 Components of DNA Regulating Transcription. W in the TATA box sequence can be either A or T.<\/em><\/figcaption><\/figure>\n \nRegulation During\u00a0Development<\/h1>\n<\/div>\n
The\u00a0regulation of gene expression\u00a0is extremely important\u00a0in\u00a0an organism’s early\u00a0development. Regulatory proteins must “turn on” certain genes in particular cells at just the right time, so the individual develops normal organs and organ systems. Homeobox genes are important genes that regulate development.<\/p>\n
Homeobox genes<\/a><\/strong>\u00a0are a large group of similar genes that direct the formation of many body structures during the\u00a0embryonic<\/a> stage. In humans, there are an estimated 235 functional homeobox genes. They are present on every chromosome and generally grouped in clusters. Homeobox genes contain instructions for making chains of 60\u00a0amino acids<\/a>, called\u00a0homeodomains<\/a><\/strong>. Proteins containing homeodomains are\u00a0transcription factors\u00a0that bind to and control the activities of other genes. The homeodomain is the part of the protein that binds to the target gene and controls its expression.<\/p>\n
\nGene Expression and\u00a0Cancer<\/h1>\n<\/div>\n
Figure 5.9.4 This flow chart shows how a series of mutations in tumor-suppressor genes and proto-oncogenes leads to cancer.<\/em><\/figcaption><\/figure>\n Some types of cancer <\/a>occur because of mutations in the genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes: proto-oncogenes and tumor-suppressor genes. Both are shown in Figure 5.9.4.<\/p>\n
- \n
- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car’s accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can’t be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n<\/ul>\n
<\/p>\n
<\/p>\n
\n\n\n 5.9 Summary<\/span><\/h1>\n<\/header>\n
\n- \n
- Using a gene<\/a> to make a protein<\/a> is called gene expression<\/a>. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of\u00a0protein synthesis<\/a>\u00a0or processing.<\/li>\n
- The regulation of transcription<\/a> is controlled by regulatory proteins <\/a>that bind to regions of DNA called regulatory elements<\/a>, which are usually located near promoters<\/a>. Most regulatory proteins are either activators<\/a> that promote transcription, or repressors<\/a> that impede transcription.<\/li>\n
- A regulatory\u00a0element\u00a0common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.<\/li>\n
- Regulation of gene expression\u00a0is extremely important during an organism’s early development. Homeobox genes<\/a> \u2014 which encode for chains of\u00a0amino acids\u00a0called homeodomains<\/a> \u2014 are important genes that regulate development.<\/li>\n
- Some types of cancer<\/a> occur because of\u00a0mutations<\/a>\u00a0in the genes that control the\u00a0cell cycle<\/a>. Cancer-causing mutations most often occur in two types of regulatory genes: tumor-suppressor genes and proto-oncogenes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n\n 5.9 Review Questions<\/span><\/h1>\n<\/header>\n
\n- \n
- Define gene expression.<\/li>\n
- Why must gene expression be regulated?<\/li>\n
- Explain how regulatory proteins may activate or repress transcription.<\/li>\n
- \n\n
- The regulation of transcription<\/a> is controlled by regulatory proteins <\/a>that bind to regions of DNA called regulatory elements<\/a>, which are usually located near promoters<\/a>. Most regulatory proteins are either activators<\/a> that promote transcription, or repressors<\/a> that impede transcription.<\/li>\n
- Tumor suppressor genes <\/strong>are genes that normally slow down or stop\u00a0cell division. When a\u00a0mutation\u00a0occurs in a tumor suppressor gene, it can no longer control cell division. This is like a car without brakes. The car can’t be slowed or stopped.\u00a0A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n<\/ul>\n
- Proto-oncogenes <\/strong>are genes that normally help cells divide. When a proto-oncogene mutates to become an oncogene, it is continuously expressed, even when it is not supposed to be. This is like a car’s accelerator pedal being stuck at full throttle. The car keeps racing at top\u00a0speed. A cell, in this case,\u00a0keeps dividing out of control, which can lead to cancer.<\/li>\n
![Stem_cell_differentiation.svg<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Stem_cell_differentiation.svg\"){kind=link}
![TATA_box_description<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:TATA_box_description.png\"){kind=link}