A Repressible Operon is Usually Controlled By

Question

A repressible operon is usually controlled by:
A) an inactive repressor that allows it to be in the "on" state
B) the supply of the precursor product for the enzymes
C) an inactive repressor that keeps it in the "off" state
D) tryptophan
E) being turned "on," usually by the end product of the pathway

Accepted Answer

In a repressible operon, such as the trp operon, the operon is usually in the "on" state because the repressor is inactive. When the end product (like tryptophan) is abundant, it activates the repressor to turn the operon "off."