Which of These Controls the Expression of the Lac Operon

Question

Which of these controls the expression of the lac operon?
A)An activator protein only.
B)An attenuation mechanism.
C)A repressor protein only.
D)Both repression and activation mechanisms.
E)Both repression and attenuation mechanisms.

Accepted Answer

The lac operon is controlled by both repression and activation mechanisms. A repressor protein can bind to the operator to prevent transcription, and an activator protein (cAMP receptor protein when bound to cAMP) enhances the binding of RNA polymerase to the promoter, facilitating transcription.