Illustrate and explain an operon that is subject to both positive and negative control containing the operator region, the operon, the promoter, the activator binding site, and the functional genes in a DNA sequence
Also compare and contrast the roles activators and repressors have in regulating the illustrated operon.
What will be an ideal response?
Answer: A combination of Figure 7.8 in the textbook illustrates the lac operon in the following order: promoter, operator, and functional genes (5' to 3') and Figure 7.9 shows the mal operon with the activator binding site, promoter, and functional genes (5' to 3'). The complete order for both control systems is: activator binding site, promoter, operator, and functional genes (5' to 3'). For the operon to be subject to a repressor blocking RNA polymerase activity, it must be downstream of the promoter site. The positive control (activator) does not necessarily have to be proximal to the promoter and can be distant so long as the sequence can fold to recruit RNA polymerase. In both cases these regulators can also be controlled by other (inducer and corepressor) molecules. They are both unified in their overall control of functional gene transcription.
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