Use the following choices to answer the question:
a. Catabolite repression
b. DNA polymerase
c. Induction
d. Repression
e. Translation


Mechanism by which the presence of glucose inhibits the lac operon.

Catabolite repression is a regulatory mechanism in bacteria where the presence of a preferred carbon source, like glucose, inhibits the expression of genes involved in the metabolism of alternative sugars. In the lac operon, glucose lowers cAMP levels, preventing activation of the CAP protein, thus repressing lac operon transcription.

The lac operon controls the metabolism of lactose in E. coli and is regulated by both induction and repression mechanisms. When glucose is absent and lactose is present, the operon is induced to produce enzymes for lactose utilization; glucose presence inhibits this process through catabolite repression.

Cyclic AMP (cAMP) binds to the catabolite activator protein (CAP) to form a complex that enhances RNA polymerase binding to the lac operon promoter. Glucose reduces intracellular cAMP levels, preventing CAP binding and thus inhibiting transcription of the lac operon.