A point mutation in the operator of the lac operon would most likely cause
A) no transcription of the lactose metabolizing genes, even when lactose is absent.
B) no transcription of the lactose metabolizing genes, even when lactose is present.
C) no binding of the repressor protein to the operator, even when lactose is absent.
D) binding of the repressor protein to the regulatory gene in both the presence and absence of lactose.
E) no transcription of the regulatory gene, even in the presence of lactose.

Question

Quizplus · Accepted Answer

A point mutation in the operator of the lac operon can prevent the repressor protein from binding to the operator, which would lead to continuous transcription of the lactose metabolizing genes, even when lactose is absent. This is because the repressor, when unable to bind to the mutated operator, cannot block RNA polymerase from transcribing the genes necessary for lactose metabolism.

A Point Mutation in the Operator of the Lac Operon