Question

Name the repressor of the lac operon.

Hint:

The lacI gene codes for the repressor protein, which regulates the lac operon in response to the presence or absence of lactose.

Answer 1

The lac operon stays switched off until lactose is available because a protein encoded by the lacI gene, called the lac repressor, sits on the operator and blocks transcription. Lactose (as allolactose) binds this repressor and removes the block, so the repressor of the lac operon is the lacI-encoded lac repressor protein.