biology-class-12-unit-06-chapter-10-genetics-and-evolution-molecular-basis-of-inheritance-l-10-12-rmphnv-p7x8

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<h3 id="successregulation-of-gene-expression-in-bacteriasuccess"><Success>Regulation of gene expression in bacteria</Success></h3>
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<p><strong>Terminology…</strong></p>
<ul>
<li><strong>Regulator Gene:</strong> A gene that regulates the expression of one or more structural genes</li>
<li><strong>Structural gene:</strong> One that forms templates for messenger RNA and is thereby responsible for the amino acid sequence of specific polypeptides</li>
<li><strong>Constitutive Gene:</strong> Genes that are required for the maintenance of basic cellular function, and are <ins>expressed</ins> in all cells of an organism under normal conditions</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-10-genetics-and-evolution-molecular-basis-of-inheritance-l-10_12-rmphnv_p7x8-023-0247.2.jpg"></p>
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<h3 id="successregulation-of-gene-expression-in-bacteriasuccess-1"><Success>Regulation of gene expression in bacteria</Success></h3>
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<p><strong>Continue…</strong></p>
<ul>
<li>
<p><strong>Operator:</strong> An operator is a segment of <ins>DNA</ins> to which a <ins>transcription</ins> factor binds to regulate <ins>gene expression</ins> by repressing it.</p>
</li>
<li>
<p><strong>Repressor:</strong> A repressor is a <ins>DNA</ins> or <ins>RNA</ins>- binding protein that inhibits the <ins>expression</ins> of one or more genes by binding to the operator or associated <ins>silencers</ins>.</p>
</li>
</ul>
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<h3 id="successwhat-is-operonsuccess"><Success>What is operon?</Success></h3>
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<ul>
<li>An <strong>operon</strong> is a functioning unit of genomic DNA containing a cluster of <ins>genes</ins> under the control of a single <ins>promoter</ins></li>
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<h5 id="or"><strong>or</strong></h5>
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<ul>
<li>A group of bacterial structural genes that are transcribed together (along with their promoter and additional sequences that control transcription) is called an <strong>operon</strong></li>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-10-genetics-and-evolution-molecular-basis-of-inheritance-l-10_12-rmphnv_p7x8-030-0446.4.jpg"></p>
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<h3 id="successorganization-of-lac-genessuccess-1"><Success>Organization of Lac Genes</Success></h3>
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<ul>
<li>
<p>The enzymes -beta galactosidase, permease, and transacetylase are encoded by adjacent structural genes in the lac operon of <em>E. coli</em></p>
</li>
<li>
<p>Beta-Galactosidase is encoded by the lacZ gene</p>
</li>
<li>
<p>permease by the lacy gene, and transacetylase by the lacx gene</p>
</li>
<li>
<p>In the lac operon, the lac Z, lac Y, and lac a genes have a common promoter</p>
</li>
<li>
<p>Upstream of the promoter is a regulator gene, lac I, which has its own promoter (P)</p>
</li>
<li>
<p>The lacl gene is transcribed into a short mRNA that is translated into a repressor Protein</p>
</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-10-genetics-and-evolution-molecular-basis-of-inheritance-l-10_12-rmphnv_p7x8-073-1004.4.jpg"></p>
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<h3 id="successregulation-of-lac-operonsuccess-1"><Success>Regulation of Lac operon</Success></h3>
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<ul>
<li>When lactose is present</li>
<li>Some of lactose is converted into allolactose</li>
<li>Allolactose binds to the repressor</li>
<li>Causes the repressor to be released from the DNA- The repressor is inactivated</li>
<li>Binding of RNA polymerase is no longer blocked</li>
<li>Transcription of lacZ, lacy, and lac a takes place, and the lac enzymes are produced</li>
<li>Genes are Switched ON</li>
</ul>
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<h3 id="successrole-of-cyclic-amp-in-lac-operonsuccess"><Success>Role of cyclic AMP in Lac Operon</Success></h3>
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<p><strong>Repressible Operon</strong></p>
<ul>
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<p>Operons is normally turned on and must be repressed</p>
</li>
<li>
<p>The trp operon contains five structural genes (trpE, trpD, trpC, trpB, and trpA)</p>
</li>
<li>
<p>These produce components of three enzymes (two of the enzymes consist of two polypeptide chains)</p>
</li>
<li>
<p>Upstream of the structural genes is the trp promoter</p>
</li>
</ul>
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<h3 id="successorganization-of-trp-genessuccess"><Success>Organization of trp genes</Success></h3>
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<p><strong>Trp E-</strong> Anthranilate Synthetase (I)</p>
<p><strong>Trp D-</strong> Anthranilate Synthetase (II) (PRA Synthetase)</p>
<p><strong>Trp C-</strong> PRA-Isomerase InGP Synthetase</p>
<p><strong>Trp B-</strong> TryPetophen Synthetase B</p>
<p><strong>Trp A-</strong> Tryptophan Synthetase</p>
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<h3 id="successmrna-transcriptional-controlsuccess-1"><Success>mRNA Transcriptional Control</Success></h3>
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<p><strong>Role of Chromatin in Regulating Transcription</strong></p>
<p><strong>Chromatin Remodeling</strong></p>
<ul>
<li>Involves enzymes that modify nucleosome by acetylation and deacetylation</li>
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<ol>
<li>
<p>Histone Acetyl transferase enzyme</p>
</li>
<li>
<p>ATP dependent nucleosome remodeling complex</p>
</li>
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<h3 id="successmrna-degradation-controlsuccess"><Success>mRNA degradation Control</Success></h3>
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<p><strong>Processing of pre mRNA control</strong></p>
<p>Includes-</p>
<ul>
<li>Alternative polyadenylation site</li>
<li>Alternative splicing site</li>
</ul>
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<p><strong>Translational Control</strong></p>
<p>RNA Interference which includes-</p>
<ul>
<li>Micro RNA (mi RNA)</li>
<li>Short Interfering RNA (siRNA)</li>
</ul>


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