There is a mutation in the operator of the lac operon in a cell such that the lac repressor always stays bound to the operator. If lactose is added to the cell, what will happen?
A) Lactose will bind to the repressor, and lac enzymes will be produced.
B) Lactose will bind to the repressor, and lac enzymes will not be produced.
C) Lactose will not bind to the repressor, and lac enzymes will be produced.
D) Lactose will bind to the operator, and lac enzymes will be produced.

Question

Quizplus · Accepted Answer

If the lac repressor always stays bound to the operator due to a mutation, it means that even in the presence of lactose, the repressor will not be released from the operator. This will prevent the transcription of the lac genes as the repressor will continue to block the RNA polymerase from accessing the promoter region. Therefore, even if lactose is added, lac enzymes will not be produced.

There Is a Mutation in the Operator of the Lac