{"id":4594,"date":"2017-04-10T20:16:33","date_gmt":"2017-04-10T20:16:33","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-biology1\/?page_id=4594"},"modified":"2017-04-10T20:16:33","modified_gmt":"2017-04-10T20:16:33","slug":"activators-and-repressors","status":"publish","type":"page","link":"https:\/\/courses.lumenlearning.com\/wm-biology1\/activators-and-repressors\/","title":{"rendered":"Activators and Repressors"},"content":{"rendered":"<p>There are two different types of gene regulation: positive and negative. Activators (and sometimes inducers) instigate positive regulation, and repressors instigate negative regulation. When an activator or inducer binds to an operon, the transcription process\u00a0either\u00a0increases in rate or is allowed to continue. When a repressor binds\u00a0to an operon, the transcription process is slowed or halted.<\/p>\n<div class=\"textbox exercises\">\n<h3>Practice Question<\/h3>\n<p>Imagine there&#8217;s a regulatory molecule that attaches to the operon when a specific protein is present. When this regulatory molecule attaches itself to the operon,\u00a0transcription is\u00a0stopped. What type of regulatory molecule is this?<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"2\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q369186\">Show Answer<\/span><\/p>\n<div id=\"q369186\" class=\"hidden-answer\" style=\"display: none\">This is an example of a repressor.<\/div>\n<\/div>\n<\/div>\n<h2>Activator<\/h2>\n<p>One example of an activator is the protein\u00a0CAP. In the presence of cAMP, CAP binds to the promoter and increases RNA polymerase activity.\u00a0In the absence of cAMP, CAP does not bind to the promoter. Transcription occurs at a low rate.<\/p>\n<div class=\"textbox exercises\">\n<h3>Practice Question<\/h3>\n<p>What is the role of an activator?<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"2\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q550409\">Show Answer<\/span><\/p>\n<div id=\"q550409\" class=\"hidden-answer\" style=\"display: none\">to enable\u00a0or increase the\u00a0transcription of a certain protein<\/div>\n<\/div>\n<\/div>\n<h3>Repressor<\/h3>\n<p>When an amino acid is present, it associates with the\u00a0<i>met<\/i>\u00a0repressor, and the repressor is activated. RNA synthesis is blocked by the presence of the repressor on the DNA strand. When the amino acid is not present, the repressor dissociates from the operator and RNA synthesis proceeds.<\/p>\n<p>When tryptophan is not present in the cell, the repressor by itself does not bind to the operator; therefore, the operon is active and tryptophan is synthesized. But when a cell has plenty of tryptophan, it doesn&#8217;t need to synthesize more. So the repressor is triggered (by the presence of plenty of tryptophan), thus turning off further synthesis of tryptophan.<\/p>\n<div class=\"textbox exercises\">\n<h3>PRactice Question<\/h3>\n<p>What is the role of a repressor?<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"2\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q669996\">Show Answer<\/span><\/p>\n<div id=\"q669996\" class=\"hidden-answer\" style=\"display: none\">to limit or restrict the transcription of a certain protein. Remember: a repressor must be turned on before it can turn synthesis\u00a0off (or down)<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox exercises\">\n<h3>Practice Questions<\/h3>\n<p>When you remove a repressor from an operon, what\u00a0would happen?<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"2\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q619621\">Show Answer<\/span><\/p>\n<div id=\"q619621\" class=\"hidden-answer\" style=\"display: none\">If you remove a repressor from an operon, transcription will occur more rapidly than the cell needs: there is nothing to prevent (or repress) the transcription<\/div>\n<\/div>\n<p>What\u00a0would happen if you remove an activator?<\/p>\n<p><textarea aria-label=\"Your Answer\" rows=\"2\"><\/textarea><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q350079\">Show Answer<\/span><\/p>\n<div id=\"q350079\" class=\"hidden-answer\" style=\"display: none\">If you remove an activator from an operon, transcription will more slowly than the cell needs: there is nothing to activate transcription.<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>There are two different types of gene regulation: positive and negative. Activators (and sometimes inducers) instigate positive regulation, and repressors instigate negative regulation. When an activator or inducer binds to an operon, the transcription process\u00a0either\u00a0increases in rate or is allowed to continue. When a repressor binds\u00a0to an operon, the transcription process is slowed or halted.<a class=\"more-tag\" href=\"https:\/\/courses.lumenlearning.com\/wm-biology1\/activators-and-repressors\/\"> Read more &raquo;<\/a><\/p>\n","protected":false},"author":17,"featured_media":0,"parent":0,"menu_order":5,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-4594","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/pages\/4594","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/users\/17"}],"replies":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/comments?post=4594"}],"version-history":[{"count":1,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/pages\/4594\/revisions"}],"predecessor-version":[{"id":4595,"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/pages\/4594\/revisions\/4595"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology1\/wp-json\/wp\/v2\/media?parent=4594"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}