In spite of its name, catabolite repression is a type of positive control in the lac operon. The catabolite activator protein (CAP), complexed with cAMP, binds to a site near the promoter and stimulates the binding of RNA polymerase. Cellular levels of cAMP are controlled by glucose; a low glucose level increases the abundance of cAMP and enhances the transcription of the lac structural genes.
-What is the effect of high levels of glucose on the lac operon?
A) Transcription is stimulated.
B) Little transcription takes place.
C) Transcription is not affected.
D) Transcription may be stimulated or inhibited, depending on the levels of lactose.

Question

Quizplus · Accepted Answer

High levels of glucose decrease cAMP levels, preventing CAP from binding to the promoter region, which results in little transcription of the lac operon.

In Spite of Its Name, Catabolite Repression Is a Type