If the gene encoding the lac repressor is mutated such that the repressor can no longer bind the operator, will transcription of that operon occur?
A) Yes, because the repressor transcriptionally activates the lac genes.
B) Yes, but only when lactose is present.
C) No, because RNA polymerase is needed to transcribe the genes.
D) Yes, because RNA polymerase will be able to bind the promoter and transcribe the operon.
E) No, because cAMP levels are low when the repressor is nonfunctional.

Question

Quizplus · Accepted Answer

The lac repressor binds to the operator region of the lac operon and prevents RNA polymerase from binding to the promoter and transcribing the genes. If the lac repressor cannot bind to the operator due to a mutation, then RNA polymerase will be able to bind to the promoter and transcribe the operon. The presence of lactose will further increase transcription by decreasing the affinity of the repressor for the operator, but it is not necessary for transcription to occur. The repressor does not transcriptionally activate the lac genes but instead acts as a negative regulator. The level of cAMP is not directly affected by the lac repressor mutation.

If the Gene Encoding the Lac Repressor Is Mutated Such