{"id":213721,"date":"2025-05-12T08:28:22","date_gmt":"2025-05-12T08:28:22","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=213721"},"modified":"2025-05-12T08:28:24","modified_gmt":"2025-05-12T08:28:24","slug":"suppose-an-operon-has-the-following-characteristics","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/05\/12\/suppose-an-operon-has-the-following-characteristics\/","title":{"rendered":"Suppose an operon has the following characteristics"},"content":{"rendered":"\n

Suppose an operon has the following characteristics: (1) The operon codes for structural proteins that convert compound Q to compound B. (2) The operon is controlled by a constitutively expressed regulatory gene called reg. (3) In wild-type individuals, the operon is transcribed in the absence of compound B but not in the presence of compound B. (4) In reg- mutants, the operon is constitutively transcribed. Is this operon inducible or repressible? Why?<\/p>\n\n\n\n

The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n

The correct answer is: Repressible operon<\/strong>.<\/p>\n\n\n\n

Explanation:<\/h3>\n\n\n\n

An operon can be either inducible<\/strong> or repressible<\/strong> depending on how it is regulated by external or internal stimuli.<\/p>\n\n\n\n

    \n
  • Inducible operons<\/strong> are usually off<\/strong> but can be turned on<\/strong> in the presence of a specific inducer (e.g., the lac operon<\/strong>).<\/li>\n\n\n\n
  • Repressible operons<\/strong> are typically on<\/strong> but can be turned off<\/strong> when a specific corepressor is present (e.g., the trp operon<\/strong>).<\/li>\n<\/ul>\n\n\n\n

    Let\u2019s analyze the scenario:<\/p>\n\n\n\n

      \n
    1. The operon codes for enzymes that convert compound Q to compound B.<\/strong>
      This suggests compound B is the end product<\/strong> of the pathway.<\/li>\n\n\n\n
    2. The operon is regulated by a constitutively expressed gene called reg.<\/strong>
      This means the reg<\/strong> gene is always transcribed and translated, producing a regulatory protein<\/strong> continuously.<\/li>\n\n\n\n
    3. In wild-type individuals, the operon is transcribed in the absence of compound B but not in its presence.<\/strong>
      This is key. It indicates that compound B, when present, inhibits<\/strong> transcription. Thus, compound B is likely acting as a corepressor<\/strong>. It binds to the regulatory protein (produced by reg), converting it into an active repressor<\/strong> that blocks operon transcription.<\/li>\n\n\n\n
    4. In reg\u207b mutants, the operon is constitutively transcribed.<\/strong>
      In these mutants, the regulatory protein is nonfunctional or absent. Without it, compound B can\u2019t exert its repressive effect. As a result, the operon remains on<\/strong> regardless of compound B\u2019s presence, confirming that reg encodes a repressor<\/strong>.<\/li>\n<\/ol>\n\n\n\n

      This system aligns with a repressible operon model<\/strong>, where the operon is normally on<\/strong> but can be turned off<\/strong> in the presence of the end product (compound B), which acts as a feedback inhibitor.<\/p>\n\n\n\n

      Thus, the operon is repressible<\/strong>, and compound B serves as a corepressor<\/strong> working with the regulatory protein to inhibit transcription when sufficient product has been synthesized.<\/p>\n","protected":false},"excerpt":{"rendered":"

      Suppose an operon has the following characteristics: (1) The operon codes for structural proteins that convert compound Q to compound B. (2) The operon is controlled by a constitutively expressed regulatory gene called reg. (3) In wild-type individuals, the operon is transcribed in the absence of compound B but not in the presence of compound […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-213721","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/213721","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=213721"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/213721\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=213721"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=213721"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=213721"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}