Note that this assignment is worth 4 points. 1. Consider the lac operon in E. coli. If both the lac operator and lac CAP binding site were mutated so that neither could bind the corresponding regulatory protein (ie, the lac repressor and CAP protein, respectively), would transcription of the lac operon be turned on or off under the condition in which there is, at the same time, the presence of lactose and the absence of glucose? Why? (Be careful with this one!) 2. Explain precisely why the control of gene expression by transcription factors in eukaryotes is an example of positive, and not negative, control of transcription. 1. Transcription of the lac operon would be turned on if lactose was present and glucose was not. This would occur even if it was mutated and there was a CAP binding site. If the glucose is absent the CAMP levels are high. If this occurs then the CAP-CAMP complex is present on the CAP binding site in the promoter region. However, if a mutation occurs then this region is changed. The CAP-
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