An operon is controlled by a repressor. When the repressor binds to a small molecule, it binds to DNA near the operon. The operon is constitutively expressed if a mutation prevents the repressor from binding to the small molecule. The type of control illustrated is:
A) negative inducible.
B) negative repressible.
C) positive inducible.
D) positive repressible.
E) catabolite repression.

Question

Quizplus · Accepted Answer

The repressor prevents transcription of the operon when it is bound to the small molecule. When the repressor is unable to bind to the small molecule, the operon is constitutively expressed. This is an example of negative repressible control.

An Operon Is Controlled by a Repressor