Question

Transcription of the lac operon is subject to positive control by CAP. CAP must be bound to which of the following in order for DNA to bind?

1) Promoter region
2) Operator region
3) Enhancer region
4) Terminator region

Answer 1

CAP, when bound to cAMP, activates transcription by binding to the promoter region of the lac operon, not the operator, enhancer, or terminator regions.

Step-by-step explanation:

In the regulation of the lac operon, CAP (CAMP-bound catabolite activator protein) serves as a positive regulator for transcription. For transcription of the lac operon to be initiated, CAP must be bound to cAMP, and this activated CAP-cAMP complex then binds to the promoter region of the lac operon. This binding facilitates the recruitment of RNA polymerase to the promoter region, enabling the transcription of genes necessary for the metabolism of lactose when glucose levels are low.

When cellular levels of glucose are low, the intracellular concentration of cAMP rises, leading to the binding of cAMP to CAP. This complex then binds to the promoter region, not the operator region, the enhancer region, or the terminator region. It essentially increases the affinity of RNA polymerase for the promoter, which boosts the transcription of the lac operon, allowing the cell to utilize lactose as an energy source.

must be bound to cAMP for DNA to bind to the promoter region of the lac operon.