Synthesis of a repressible enzyme is inhibited by
A)Repressor alone bound to operator
B)Substrate bound to repressor
C)Substrate bound to promoter
D)Corepressor and repressor binding to operator
E)None of the choices are correct

Question

Quizplus · Accepted Answer

The presence of a corepressor and repressor bound to the operator region will inhibit the synthesis of the enzyme. The corepressor, which is often a product of the same pathway as the enzyme, binds to the repressor and activates it. The activated repressor then binds to the operator, preventing RNA polymerase from binding to the promoter and transcribing the gene. The inhibition of enzyme synthesis is therefore conditional upon the presence of the corepressor, which indicates that the pathway does not require additional enzyme production. This is an example of negative regulation of gene expression.

Synthesis of a Repressible Enzyme Is Inhibited by