Essential Biochemistry - Regulation Of Gene Expression And Mutation (Section 1 - No. 2)
Which of the following statements about the regulation of the lac operon is correct?
In the absence of glucose and lactose, the repressor binds to the operator.
In the presence of glucose and absence of lactose, the repressor binds to the operator.
In the presence of glucose and lactose, CAP binds to the CAP-binding site.
In the presence of lactose and absence of glucose, the repressor is inactive.
Explanation
When glucose is present and lactose is absent, the repressor binds and the operon is off. In the presence of lactose and absence of glucose, lactose inactivates the repressor.
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