In the lac operon the repressor allows transcription to occu

In the lac operon, the repressor allows transcription to occur when _______.

A.

the repressor is not bound to the inducer.

B.

the repressor is bound to glucose.

C.

the repressor is not bound to the lacZ.

D.

the repressor is bound to the inducer.

Solution

The correct answer is choice D.

Explanation: Lac operon is an inducible operon which comprises of a repressor. The repressor normally masks the operator and thus prevents transcription. However, in the presence of appropriate substrate i.e. lactose, the operon switches \"on\". When lactose is present, the repressor would be inactivated and won\'t be able to mask the operator gene of the cistron. This will promote free lateral movement of RNA polymerase over the cistron and thus, transcription and translation of lac-genes takes place. Further, low levels of glucose also promote operativity of lac operon. Thus, release of repressor from the operator and its subsequent binding to the inducer promotes transcription.