12-Prokaryotes - Gene Regulation in Prokaryotes the lac...

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Gene Regulation in Prokaryotes the lac operon the trp operon Method : the electrophoretic mobility shift assay attenuation the ara operon
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The mechanisms of gene regulation, or genetic control, determine where, when, and how much a gene is expressed . every gene has an RNA-coding region ( transcribed region ) and nearby regulatory region (s) ( not transcribed ) DNA binding proteins recognize specific sequences on the regulatory region of the gene and either activate or repress the transcription of the coding region Gene regulation
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An operon is a set of structural genes with related functions under the control of a common regulatory region that responds to changing conditions in the cell . occurs only in prokaryotes Operon The lac operon the products of the structural genes of this operon are involved in the utilization of lactose for energy these genes will only be expressed when lactose is present, but also only if the cell needs to use lactose for energy glucose is the preferred source of energy in the cell, therefore : the genes of the lac operon are expressed only if glucose levels are low and lactose levels are high
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Transcription of the polycistronic mRNA from the structural genes of lac operon
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Function of the gene product of lacZ β -galactosidase hydrolyzes lactose into galactose and glucose, which can enter glycolysis to harvest energy for the cell.
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Other structural gene products of lac operon lacY gene product: a permease facilitates the entry of lactose into the bacterial cell lacA gene product: a transacetylase thought to be involved in the removal of by-products of lactose digestion from the cell
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Chromosomal components of the lac operon Structural genes under operon control: lacZ , lacY , and lacA Control regions : i gene : codes for the repressor protein operator ( not a gene! ): binding site for the repressor protein promoter : binding site for RNA polymerase
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The state of the lac operon in the absence of lactose if the repressor binds to the operator: repressor blocks RNA
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12-Prokaryotes - Gene Regulation in Prokaryotes the lac...

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