Question

If there are mutations that inactivate lacP and lacI, which of the following is true? (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator).

a) Lac operon is constitutively expressed
b) Lac operon is not expressed
c) Lac operon is inducible
d) Lac operon is repressed

Answer 1

If there are mutations that inactivate lacP and lacI, the lac operon would be constitutively expressed.

Step-by-step explanation:

If there are mutations that inactivate lacP and lacI, the lac operon would be constitutively expressed. These mutations would prevent the lac repressor protein from being made and from binding to the operator DNA. Without the repressor blocking its movement, the RNA polymerase would be able to transcribe the operon, resulting in the continuous expression of the lac genes. This would allow for the production of the proteins involved in lactose metabolism even in the absence of lactose.