Question

In the lac operon of E.coli, which of the following happens when the repressor binds to the operator?

Answer 1

When lactose concentration in the medium is low, the repressor binds to the operator in such a way that RNA polymerase is prevented from binding to the promoter. This prevents transcription of the structural genes by RNA polymerase.

Thus, repressors ensure that transcription of the genes happens only when required. In the absence of lactose, the enzymes to digest it would not be required and hence, transcription is prevented.