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.


1 Answer 1


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.

  • $\begingroup$ What is the meaning of "the operator is never closed" ? $\endgroup$
    – biogirl
    Jan 28, 2014 at 10:02
  • 1
    $\begingroup$ I have expanded my answer. $\endgroup$
    – Chris
    Jan 28, 2014 at 10:13

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