If the gene encoding the lac repressor is mutated so 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

If the lac repressor is unable to bind to the operator, it will not block RNA polymerase from transcribing the genes. Therefore, transcription will occur when the promoter is recognized by RNA polymerase. However, the presence of lactose is still needed to induce the expression and full activity of the genes. Low cAMP levels are not directly related to the lac repressor function.

If the Gene Encoding the Lac Repressor Is Mutated So