The Lac Operon also has Positive Control

The Lac Operon also has Positive Control - The Lac Operon...

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The Lac Operon also has Positive Control In addition to the negative control mechanism described earlier in this chapter, the lac operon is also regulated by a positive control mechanism. E. coli prefer glucose when both glucose and lactose are present. When allolactose binds to and inhibits the repressor, the genes that code for enzymes needed to digest lactose are transcribed but only at a low level. Much of the cell's energy comes from glucose instead of lactose. When the level of glucose is low, the level of cAMP increases. Cyclic AMP activates a molecule (CAP), which then binds to the lac promoter and enhances the rate of transcription. Promoters and Sigma Factors The nucleotide sequence of promoters is similar but not identical. The more similar the sequence is to a consensus sequence, the more likely that RNA polymerase will attach and produce mRNA from the associated genes. Part of the RNA polymerase enzyme that recognizes the promoter is called the sigma factor. After transcription begins, this unit dissociates from the enzyme.
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The Lac Operon also has Positive Control - The Lac Operon...

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