Note also that evoluon could have cut out the

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Unformatted text preview: tradiol responsive genes key = activates = inhibits 5/23/11 What the logic of the regulation of the lac operon? Lactose… does what? Activate something or inhibit something (this is a tricky question)? The lac repressor does what? Activate something or inhibit something? How about cAMP? CRP? Eukaryotes don’t have operons, so how can they coordinate the expression of a complete pathway? Induc/on, or ac/va/on, of a transcrip/on factor can result in the simultaneous ac/va/on of many downstream genes ­ those genes simply need to share the DNA sequence (at the promoter, or the enhancer) that is recognized by the induced TF. Note there are two completely different TFs in this model… 5/23/11 The first step in this pathway must be triggered by a TF that can detect the stress. Note also that this TF must be expressed cons/tu/vely ­ at least at some level, even in the absence of the stress. Note also that evolu/on could have cut out the middleman and had this stress ­sensi/ve protein bind directly to the target genes ­ I wonder why it didn’t evolve that way? Note also that the SECOND transcrip/on factor doesn’t have to detect the stress at all. Its transcrip/onal induc/on by stress is sufficient to correctly modulate the downstream response. Note that other transcrip/on factors might be among the genes induced ­...
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This note was uploaded on 05/17/2013 for the course BIS 100 taught by Professor Charles during the Winter '11 term at UC Davis.

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