Question

Which of the following is FALSE regarding CAP?

A. Most CAP-dependent promoters have a good match to the -35 site consensus.

B. Class II CAP-dependent promoters always have a single binding site for the CAP dimer located at position -41.5.

C. In the Lac promoter, CAP binding increases formation of the closed promoter complex.

Answer 1

The false statement about CAP in the context of the lac operon is that Class II CAP-dependent promoters always have a single CAP dimer binding site located at position -41.5. This is incorrect as the exact position can vary among different promoters. Option B.

Step-by-step explanation:

The statement that is FALSE regarding CAP (catabolite activator protein) in the context of the lac operon is B. 'Class II CAP-dependent promoters always have a single binding site for the CAP dimer located at position -41.5.'

This statement is incorrect because the binding site for the CAP dimer can vary among different class II CAP-dependent promoters. The precise position of the CAP binding site is important for the regulation of gene expression but is not universally fixed at -41.5 for all class II promoters.

In the Lac operon, CAP interacts with cAMP (cyclic AMP) to form a complex that binds to the lac promoter region. This binding facilitates the RNA polymerase's interaction with the promoter, thereby increasing the transcription of genes involved in lactose metabolism when glucose is absent.

The presence of lactose leads to the formation of allolactose, which removes the lac repressor protein, allowing transcription to proceed in conjunction with the cAMP-CAP activation.

So Option B is correct.

Answer 2

The false statement about CAP in the context of the lac operon is that Class II CAP-dependent promoters always have a single CAP dimer binding site located at position -41.5. This is incorrect as the exact position can vary among different promoters. Option B.

Step-by-step explanation:

The statement that is FALSE regarding CAP (catabolite activator protein) in the context of the lac operon is B. 'Class II CAP-dependent promoters always have a single binding site for the CAP dimer located at position -41.5.'

This statement is incorrect because the binding site for the CAP dimer can vary among different class II CAP-dependent promoters. The precise position of the CAP binding site is important for the regulation of gene expression but is not universally fixed at -41.5 for all class II promoters.

In the Lac operon, CAP interacts with cAMP (cyclic AMP) to form a complex that binds to the lac promoter region. This binding facilitates the RNA polymerase's interaction with the promoter, thereby increasing the transcription of genes involved in lactose metabolism when glucose is absent.

The presence of lactose leads to the formation of allolactose, which removes the lac repressor protein, allowing transcription to proceed in conjunction with the cAMP-CAP activation.

So Option B is correct.