Presentation13

Presentation13 - Regulationofgeneexpression

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Regulation of gene expression 1. The Lac operon in E. coli; the first example of a genetic switch. In the operon, the lacZ gene encodes beta-galactosidase, an enzyme that breaks down lactose into  glucose and galactose, the lacY gene encodes a permease, which binds to the cell membrane and allows  lactose to enter the cell, and the lacA gene makes an acetylase, which we will ignore because it is not  necessary for lactose catabolism. lacZ lacY lacA Upstream of the operon’s promoter is the lacI gene.  lacI encodes a repressor protein that can bind to  specific DNA sequences present in the lac operon promoter (p).  Binding interferes with the operon’s  expression (the transcription of the Z, Y, and A genes).  The lacI-encoded repressor protein is an  example of a “ transcription factor ”- proteins that bind to promoters and regulate gene expression.  Not 
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Presentation13 - Regulationofgeneexpression

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