Question

Which of the following is a logical explanation for why the mutation in an activator binding site causes lactase persistance?

A. The mutated DNA sequence prevents a repressor protein from binding so that RNA polymerase cannot be blocked from the promoter, allowing transcription to continue throughout an organisms life.
B. The mutated DNA sequence prevents an activator protein from binding so that RNA polymerase cannot be blocked from the promoter, allowing transcription to continue throughout an organisms life.
C. The DNA sequence helps the activator protein bind better so it continues to recruit RNA polymerase, promoting transcription of the gene throughout an organisms life.
D. The DNA sequence helps the activator protein bind better so it continues to recruit DNA polymerase, promoting transcription of the gene throughout an organisms life.

Answer 1

One site is the location where RNA polymerase binds. The second location is the binding site for a complex between the catabolite activator protein (CAP) and cyclic AMP (cAMP). The binding of the CAP-cAMP complex to the promoter site is required for transcription of the lac operon.

A  is correct option

A. The mutated DNA sequence prevents a repressor protein from binding so that RNA polymerase cannot be blocked from the promoter, allowing transcription to continue throughout an organisms life.