Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

If a constitutive mutation happens in the operator of an inducible operon, does that mean that repressors won't be able to bind them ? Or does it mean that even if repressors are bound, they will not have any effect on the gene ?

I am specifically talking about lac operon.

share|improve this question
up vote 2 down vote accepted

For the lac operon there are two possibilities for constitutive expression mutations:

  1. The operator is never closed.

Reason: Mutation of the repressor, so its not present, doesn't bind or binds only with very low affinity for the operon.

  1. The repressor can not bind.

Reason: The binding site for the repressor is mutated.

See this Website or this Website for more information.

share|improve this answer
What is the meaning of "the operator is never closed" ? – biogirl Jan 28 '14 at 10:02
I have expanded my answer. – Chris Jan 28 '14 at 10:13

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.