{"id":4024,"date":"2017-01-04T05:15:24","date_gmt":"2017-01-04T05:15:24","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-biology1\/?post_type=chapter&#038;p=4024"},"modified":"2024-04-29T16:28:44","modified_gmt":"2024-04-29T16:28:44","slug":"prokaryotic-transcription","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/wm-biology1\/chapter\/prokaryotic-transcription\/","title":{"raw":"Prokaryotic Transcription","rendered":"Prokaryotic Transcription"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Understand the basic steps in the transcription of DNA into RNA in prokaryotic cells<\/li>\r\n<\/ul>\r\n<\/div>\r\nProkaryotes do not have membrane-enclosed nuclei. Therefore, the processes of transcription, translation, and mRNA degradation can all occur simultaneously. The intracellular level of a bacterial protein can quickly be amplified by multiple transcription and translation events occurring concurrently on the same DNA template. Prokaryotic transcription often covers more than one gene and produces polycistronic mRNAs that specify more than one protein.\r\n\r\nOur discussion here will exemplify transcription by describing this process in <em>Escherichia coli<\/em>, a well-studied bacterial species. Although some differences exist between transcription in <em>E. coli<\/em> and transcription in archaea, an understanding of <em>E. coli <\/em>transcription can be applied to virtually all bacterial species.\r\n<h2>Prokaryotic RNA Polymerase<\/h2>\r\nProkaryotes use the same RNA polymerase to transcribe all of their genes. In <em>E. coli<\/em>, the polymerase is composed of five polypeptide subunits, two of which are identical. Four of these subunits, denoted <em>\u03b1<\/em>, <em>\u03b1<\/em>, <em>\u03b2<\/em>, and <em>\u03b2<\/em>\u2032 comprise the polymerase <strong>core enzyme<\/strong>. These subunits assemble every time a gene is transcribed, and they disassemble once transcription is complete. Each subunit has a unique role; the two <em>\u03b1<\/em>-subunits are necessary to assemble the polymerase on the DNA; the <em>\u03b2<\/em>-subunit binds to the ribonucleoside triphosphate that will become part of the nascent \u201crecently born\u201d mRNA molecule; and the <em>\u03b2<\/em>\u2032 binds the DNA template strand. The fifth subunit, <em>\u03c3<\/em>, is involved only in transcription initiation. It confers transcriptional specificity such that the polymerase begins to synthesize mRNA from an appropriate initiation site. Without <em>\u03c3<\/em>, the core enzyme would transcribe from random sites and would produce mRNA molecules that specified protein gibberish. The polymerase comprised of all five subunits is called the <strong>holoenzyme <\/strong>(a holoenzyme is\u00a0a biochemically active compound comprised of an enzyme\u00a0and its coenzyme).\r\n<h2>Prokaryotic Promoters<\/h2>\r\n[caption id=\"attachment_4028\" align=\"alignright\" width=\"500\"]<img class=\"wp-image-4028\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2017\/01\/04050852\/Figure_15_02_01.jpg\" alt=\"Illustration shows the \u03c3 subunit of RNA polymerase bound to two consensus sequences that are 10 and 35 bases upstream of the transcription start site. RNA polymerase is bound to \u03c3.\" width=\"500\" height=\"223\" \/> Figure 1. The \u03c3 subunit of prokaryotic RNA polymerase recognizes consensus sequences found in the promoter region upstream of the transcription start sight. The \u03c3 subunit dissociates from the polymerase after transcription has been initiated.[\/caption]\r\n\r\nA <strong>promoter<\/strong> is a DNA sequence onto which the transcription machinery binds and initiates transcription. In most cases, promoters exist upstream of the genes they regulate. The specific sequence of a promoter is very important because it determines whether the corresponding gene is transcribed all the time, some of the time, or infrequently. Although promoters vary among prokaryotic genomes, a few elements are conserved. At the -10 and -35 regions upstream of the initiation site, there are two promoter <strong>consensus\u00a0<\/strong>sequences, or regions that are similar across all promoters and across various bacterial species (Figure 1).\r\n\r\nThe -10 consensus sequence, called the -10 region, is TATAAT. The -35 sequence, TTGACA, is recognized and bound by <em>\u03c3<\/em>. Once this interaction is made, the subunits of the core enzyme bind to the site. The A\u2013T-rich -10 region facilitates unwinding of the DNA template, and several phosphodiester bonds are made. The transcription initiation phase ends with the production of abortive transcripts, which are polymers of approximately 10 nucleotides that are made and released.\r\n<div class=\"textbox shaded\">View this <a href=\"http:\/\/openstaxcollege.org\/l\/transcription\" target=\"_blank\" rel=\"nofollow noopener\">MolecularMovies animation<\/a> to see the first part of transcription and the base sequence repetition of the TATA box.<\/div>\r\n<h2>Elongation and Termination in Prokaryotes<\/h2>\r\nThe transcription elongation phase begins with the release of the <em>\u03c3<\/em> subunit from the polymerase. The dissociation of <em>\u03c3<\/em> allows the core enzyme to proceed along the DNA template, synthesizing mRNA in the 5\u2032 to 3\u2032 direction at a rate of approximately 40 nucleotides per second. As elongation proceeds, the DNA is continuously unwound ahead of the core enzyme and rewound behind it (Figure 2). The base pairing between DNA and RNA is not stable enough to maintain the stability of the mRNA synthesis components. Instead, the RNA polymerase acts as a stable linker between the DNA template and the nascent RNA strands to ensure that elongation is not interrupted prematurely.\r\n\r\n[caption id=\"attachment_4182\" align=\"aligncenter\" width=\"1024\"]<img class=\"wp-image-4182 size-large\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2017\/01\/25191457\/Figure_15_01_02a-1024x205.jpg\" alt=\"To make a protein, genetic information encoded by the DNA must be transcribed onto an mRNA molecule. The RNA is then processed by splicing to remove exons and by the addition of a 5\u2032 cap and a poly-A tail. A ribosome then reads the sequence on the mRNA, and uses this information to string amino acids into a protein.\" width=\"1024\" height=\"205\" \/> Figure 2. Click for a larger image. During elongation, the prokaryotic RNA polymerase tracks along the DNA template, synthesizes mRNA in the 5\u2032 to 3\u2032 direction, and unwinds and rewinds the DNA as it is read.[\/caption]\r\n<h2>Prokaryotic Termination Signals<\/h2>\r\nOnce a gene is transcribed, the prokaryotic polymerase needs to be instructed to dissociate from the DNA template and liberate the newly made mRNA. Depending on the gene being transcribed, there are two kinds of termination signals. One is protein-based and the other is RNA-based. <strong>Rho-dependent termination<\/strong> is controlled by the rho protein, which tracks along behind the polymerase on the growing mRNA chain. Near the end of the gene, the polymerase encounters a run of G nucleotides on the DNA template and it stalls. As a result, the rho protein collides with the polymerase. The interaction with rho releases the mRNA from the transcription bubble.\r\n\r\n<strong>Rho-independent termination<\/strong> is controlled by specific sequences in the DNA template strand. As the polymerase nears the end of the gene being transcribed, it encounters a region rich in C\u2013G nucleotides. The mRNA folds back on itself, and the complementary C\u2013G nucleotides bind together. The result is a stable <strong>hairpin<\/strong> that causes the polymerase to stall as soon as it begins to transcribe a region rich in A\u2013T nucleotides. The complementary U\u2013A region of the mRNA transcript forms only a weak interaction with the template DNA. This, coupled with the stalled polymerase, induces enough instability for the core enzyme to break away and liberate the new mRNA transcript.\r\n\r\nUpon termination, the process of transcription is complete. By the time termination occurs, the prokaryotic transcript would already have been used to begin synthesis of numerous copies of the encoded protein because these processes can occur concurrently. The unification of transcription, translation, and even mRNA degradation is possible because all of these processes occur in the same 5\u2032 to 3\u2032 direction, and because there is no membranous compartmentalization in the prokaryotic cell (Figure 3). In contrast, the presence of a nucleus in eukaryotic cells precludes simultaneous transcription and translation.\r\n\r\n[caption id=\"attachment_4030\" align=\"aligncenter\" width=\"544\"]<img class=\"size-full wp-image-4030\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2017\/01\/04051219\/Figure_15_02_03.jpg\" alt=\"Illustration shows multiple mRNAs transcribed off one gene. Ribosomes attach to the mRNA before transcription is complete and begin to make protein.\" width=\"544\" height=\"189\" \/> Figure 3. Multiple polymerases can transcribe a single bacterial gene while numerous ribosomes concurrently translate the mRNA transcripts into polypeptides. In this way, a specific protein can rapidly reach a high concentration in the bacterial cell.[\/caption]\r\n\r\n<div class=\"textbox shaded\">\r\n\r\nVisit this BioStudio animation to see the process of prokaryotic transcription.\r\n\r\nhttps:\/\/youtu.be\/WsofH466lqk\r\n\r\n<\/div>\r\n<div class=\"textbox exercises\">\r\n<h3>Practice\u00a0Questions<\/h3>\r\nWhich subunit of the <em>E. coli<\/em> polymerase confers specificity to transcription?\r\n<ol style=\"list-style-type: lower-alpha;\">\r\n \t<li><em>\u03b1<\/em><\/li>\r\n \t<li><em>\u03b2<\/em><\/li>\r\n \t<li><em>\u03b2<\/em>\u2032<\/li>\r\n \t<li><em>\u03c3<\/em><\/li>\r\n<\/ol>\r\n[reveal-answer q=\"861545\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"861545\"]The\u00a0<em>\u03c3<\/em>\u00a0subunit of the <em>E. coli<\/em> polymerase confers specificity to transcription.\r\n\r\n[\/hidden-answer]\r\n\r\nThe -10 and -35 regions of prokaryotic promoters are called consensus sequences because ________.\r\n<ol style=\"list-style-type: lower-alpha;\">\r\n \t<li>they are identical in all bacterial species<\/li>\r\n \t<li>they are similar in all bacterial species<\/li>\r\n \t<li>they exist in all organisms<\/li>\r\n \t<li>they have the same function in all organisms<\/li>\r\n<\/ol>\r\n[reveal-answer q=\"827251\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"827251\"]The -10 and -35 regions of prokaryotic promoters are called consensus sequences because they are similar in all bacterial species.[\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox learning-objectives\">\r\n<h3>In\u00a0Summary: Prokaryotic Transcription<\/h3>\r\nIn prokaryotes, mRNA synthesis is initiated at a promoter sequence on the DNA template comprising two consensus sequences that recruit RNA polymerase. The prokaryotic polymerase consists of a core enzyme of four protein subunits and a <em>\u03c3<\/em> protein that assists only with initiation. Elongation synthesizes mRNA in the 5\u2032 to 3\u2032 direction at a rate of 40 nucleotides per second. Termination liberates the mRNA and occurs either by rho protein interaction or by the formation of an mRNA hairpin.\r\n\r\n<\/div>\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assess.lumenlearning.com\/practice\/1bd9c728-bcb2-47ed-ba42-8f66c8d0255f\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Understand the basic steps in the transcription of DNA into RNA in prokaryotic cells<\/li>\n<\/ul>\n<\/div>\n<p>Prokaryotes do not have membrane-enclosed nuclei. Therefore, the processes of transcription, translation, and mRNA degradation can all occur simultaneously. The intracellular level of a bacterial protein can quickly be amplified by multiple transcription and translation events occurring concurrently on the same DNA template. Prokaryotic transcription often covers more than one gene and produces polycistronic mRNAs that specify more than one protein.<\/p>\n<p>Our discussion here will exemplify transcription by describing this process in <em>Escherichia coli<\/em>, a well-studied bacterial species. Although some differences exist between transcription in <em>E. coli<\/em> and transcription in archaea, an understanding of <em>E. coli <\/em>transcription can be applied to virtually all bacterial species.<\/p>\n<h2>Prokaryotic RNA Polymerase<\/h2>\n<p>Prokaryotes use the same RNA polymerase to transcribe all of their genes. In <em>E. coli<\/em>, the polymerase is composed of five polypeptide subunits, two of which are identical. Four of these subunits, denoted <em>\u03b1<\/em>, <em>\u03b1<\/em>, <em>\u03b2<\/em>, and <em>\u03b2<\/em>\u2032 comprise the polymerase <strong>core enzyme<\/strong>. These subunits assemble every time a gene is transcribed, and they disassemble once transcription is complete. Each subunit has a unique role; the two <em>\u03b1<\/em>-subunits are necessary to assemble the polymerase on the DNA; the <em>\u03b2<\/em>-subunit binds to the ribonucleoside triphosphate that will become part of the nascent \u201crecently born\u201d mRNA molecule; and the <em>\u03b2<\/em>\u2032 binds the DNA template strand. The fifth subunit, <em>\u03c3<\/em>, is involved only in transcription initiation. It confers transcriptional specificity such that the polymerase begins to synthesize mRNA from an appropriate initiation site. Without <em>\u03c3<\/em>, the core enzyme would transcribe from random sites and would produce mRNA molecules that specified protein gibberish. The polymerase comprised of all five subunits is called the <strong>holoenzyme <\/strong>(a holoenzyme is\u00a0a biochemically active compound comprised of an enzyme\u00a0and its coenzyme).<\/p>\n<h2>Prokaryotic Promoters<\/h2>\n<div id=\"attachment_4028\" style=\"width: 510px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-4028\" class=\"wp-image-4028\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2017\/01\/04050852\/Figure_15_02_01.jpg\" alt=\"Illustration shows the \u03c3 subunit of RNA polymerase bound to two consensus sequences that are 10 and 35 bases upstream of the transcription start site. RNA polymerase is bound to \u03c3.\" width=\"500\" height=\"223\" \/><\/p>\n<p id=\"caption-attachment-4028\" class=\"wp-caption-text\">Figure 1. The \u03c3 subunit of prokaryotic RNA polymerase recognizes consensus sequences found in the promoter region upstream of the transcription start sight. The \u03c3 subunit dissociates from the polymerase after transcription has been initiated.<\/p>\n<\/div>\n<p>A <strong>promoter<\/strong> is a DNA sequence onto which the transcription machinery binds and initiates transcription. In most cases, promoters exist upstream of the genes they regulate. The specific sequence of a promoter is very important because it determines whether the corresponding gene is transcribed all the time, some of the time, or infrequently. Although promoters vary among prokaryotic genomes, a few elements are conserved. At the -10 and -35 regions upstream of the initiation site, there are two promoter <strong>consensus\u00a0<\/strong>sequences, or regions that are similar across all promoters and across various bacterial species (Figure 1).<\/p>\n<p>The -10 consensus sequence, called the -10 region, is TATAAT. The -35 sequence, TTGACA, is recognized and bound by <em>\u03c3<\/em>. Once this interaction is made, the subunits of the core enzyme bind to the site. The A\u2013T-rich -10 region facilitates unwinding of the DNA template, and several phosphodiester bonds are made. The transcription initiation phase ends with the production of abortive transcripts, which are polymers of approximately 10 nucleotides that are made and released.<\/p>\n<div class=\"textbox shaded\">View this <a href=\"http:\/\/openstaxcollege.org\/l\/transcription\" target=\"_blank\" rel=\"nofollow noopener\">MolecularMovies animation<\/a> to see the first part of transcription and the base sequence repetition of the TATA box.<\/div>\n<h2>Elongation and Termination in Prokaryotes<\/h2>\n<p>The transcription elongation phase begins with the release of the <em>\u03c3<\/em> subunit from the polymerase. The dissociation of <em>\u03c3<\/em> allows the core enzyme to proceed along the DNA template, synthesizing mRNA in the 5\u2032 to 3\u2032 direction at a rate of approximately 40 nucleotides per second. As elongation proceeds, the DNA is continuously unwound ahead of the core enzyme and rewound behind it (Figure 2). The base pairing between DNA and RNA is not stable enough to maintain the stability of the mRNA synthesis components. Instead, the RNA polymerase acts as a stable linker between the DNA template and the nascent RNA strands to ensure that elongation is not interrupted prematurely.<\/p>\n<div id=\"attachment_4182\" style=\"width: 1034px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-4182\" class=\"wp-image-4182 size-large\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2017\/01\/25191457\/Figure_15_01_02a-1024x205.jpg\" alt=\"To make a protein, genetic information encoded by the DNA must be transcribed onto an mRNA molecule. The RNA is then processed by splicing to remove exons and by the addition of a 5\u2032 cap and a poly-A tail. A ribosome then reads the sequence on the mRNA, and uses this information to string amino acids into a protein.\" width=\"1024\" height=\"205\" \/><\/p>\n<p id=\"caption-attachment-4182\" class=\"wp-caption-text\">Figure 2. Click for a larger image. During elongation, the prokaryotic RNA polymerase tracks along the DNA template, synthesizes mRNA in the 5\u2032 to 3\u2032 direction, and unwinds and rewinds the DNA as it is read.<\/p>\n<\/div>\n<h2>Prokaryotic Termination Signals<\/h2>\n<p>Once a gene is transcribed, the prokaryotic polymerase needs to be instructed to dissociate from the DNA template and liberate the newly made mRNA. Depending on the gene being transcribed, there are two kinds of termination signals. One is protein-based and the other is RNA-based. <strong>Rho-dependent termination<\/strong> is controlled by the rho protein, which tracks along behind the polymerase on the growing mRNA chain. Near the end of the gene, the polymerase encounters a run of G nucleotides on the DNA template and it stalls. As a result, the rho protein collides with the polymerase. The interaction with rho releases the mRNA from the transcription bubble.<\/p>\n<p><strong>Rho-independent termination<\/strong> is controlled by specific sequences in the DNA template strand. As the polymerase nears the end of the gene being transcribed, it encounters a region rich in C\u2013G nucleotides. The mRNA folds back on itself, and the complementary C\u2013G nucleotides bind together. The result is a stable <strong>hairpin<\/strong> that causes the polymerase to stall as soon as it begins to transcribe a region rich in A\u2013T nucleotides. The complementary U\u2013A region of the mRNA transcript forms only a weak interaction with the template DNA. This, coupled with the stalled polymerase, induces enough instability for the core enzyme to break away and liberate the new mRNA transcript.<\/p>\n<p>Upon termination, the process of transcription is complete. By the time termination occurs, the prokaryotic transcript would already have been used to begin synthesis of numerous copies of the encoded protein because these processes can occur concurrently. The unification of transcription, translation, and even mRNA degradation is possible because all of these processes occur in the same 5\u2032 to 3\u2032 direction, and because there is no membranous compartmentalization in the prokaryotic cell (Figure 3). In contrast, the presence of a nucleus in eukaryotic cells precludes simultaneous transcription and translation.<\/p>\n<div id=\"attachment_4030\" style=\"width: 554px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-4030\" class=\"size-full wp-image-4030\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1087\/2017\/01\/04051219\/Figure_15_02_03.jpg\" alt=\"Illustration shows multiple mRNAs transcribed off one gene. Ribosomes attach to the mRNA before transcription is complete and begin to make protein.\" width=\"544\" height=\"189\" \/><\/p>\n<p id=\"caption-attachment-4030\" class=\"wp-caption-text\">Figure 3. Multiple polymerases can transcribe a single bacterial gene while numerous ribosomes concurrently translate the mRNA transcripts into polypeptides. In this way, a specific protein can rapidly reach a high concentration in the bacterial cell.<\/p>\n<\/div>\n<div class=\"textbox shaded\">\n<p>Visit this BioStudio animation to see the process of prokaryotic transcription.<\/p>\n<p><iframe loading=\"lazy\" id=\"oembed-1\" title=\"Transcription\" width=\"500\" height=\"375\" src=\"https:\/\/www.youtube.com\/embed\/WsofH466lqk?feature=oembed&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<\/div>\n<div class=\"textbox exercises\">\n<h3>Practice\u00a0Questions<\/h3>\n<p>Which subunit of the <em>E. coli<\/em> polymerase confers specificity to transcription?<\/p>\n<ol style=\"list-style-type: lower-alpha;\">\n<li><em>\u03b1<\/em><\/li>\n<li><em>\u03b2<\/em><\/li>\n<li><em>\u03b2<\/em>\u2032<\/li>\n<li><em>\u03c3<\/em><\/li>\n<\/ol>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q861545\">Show Answer<\/span><\/p>\n<div id=\"q861545\" class=\"hidden-answer\" style=\"display: none\">The\u00a0<em>\u03c3<\/em>\u00a0subunit of the <em>E. coli<\/em> polymerase confers specificity to transcription.<\/p>\n<\/div>\n<\/div>\n<p>The -10 and -35 regions of prokaryotic promoters are called consensus sequences because ________.<\/p>\n<ol style=\"list-style-type: lower-alpha;\">\n<li>they are identical in all bacterial species<\/li>\n<li>they are similar in all bacterial species<\/li>\n<li>they exist in all organisms<\/li>\n<li>they have the same function in all organisms<\/li>\n<\/ol>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q827251\">Show Answer<\/span><\/p>\n<div id=\"q827251\" class=\"hidden-answer\" style=\"display: none\">The -10 and -35 regions of prokaryotic promoters are called consensus sequences because they are similar in all bacterial species.<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox learning-objectives\">\n<h3>In\u00a0Summary: Prokaryotic Transcription<\/h3>\n<p>In prokaryotes, mRNA synthesis is initiated at a promoter sequence on the DNA template comprising two consensus sequences that recruit RNA polymerase. The prokaryotic polymerase consists of a core enzyme of four protein subunits and a <em>\u03c3<\/em> protein that assists only with initiation. Elongation synthesizes mRNA in the 5\u2032 to 3\u2032 direction at a rate of 40 nucleotides per second. Termination liberates the mRNA and occurs either by rho protein interaction or by the formation of an mRNA hairpin.<\/p>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"assessment_practice_1bd9c728-bcb2-47ed-ba42-8f66c8d0255f\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/1bd9c728-bcb2-47ed-ba42-8f66c8d0255f?iframe_resize_id=assessment_practice_id_1bd9c728-bcb2-47ed-ba42-8f66c8d0255f\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-4024\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology 2e. <strong>Provided by<\/strong>: OpenStax. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\">http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":17,"menu_order":14,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology 2e\",\"author\":\"\",\"organization\":\"OpenStax\",\"url\":\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction\"}]","CANDELA_OUTCOMES_GUID":"376b85cc-0ba1-4fb7-827d-91765bc1e268, b175ebc2-b58a-44d8-be96-c0b456168cbf","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-4024","chapter","type-chapter","status-publish","hentry"],"part":316,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters\/4024","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/users\/17"}],"version-history":[{"count":17,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters\/4024\/revisions"}],"predecessor-version":[{"id":5986,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters\/4024\/revisions\/5986"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/parts\/316"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapters\/4024\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/media?parent=4024"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/pressbooks\/v2\/chapter-type?post=4024"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/contributor?post=4024"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/license?post=4024"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}