Question

Gene regulation governing lactose operon of E.coli that involves the lac gene product is

• A. feedback inhibition because excess of $\beta$ -galactosidase can switch off transcription
• B. positive and inducible because it can be induced by lactose
• C. negative and inducible because repressor protein prevents transcription
• D. negative and repressible because repressor protein prevents transcription

Answer 1

The correct option is C negative and inducible because repressor protein prevents transcription

The operon is switched off when repressor protein produced by regulatory or inhibitory gene binds to operator gene. RNA polymerase gets blocked, so there would be no transcription. Regulation of lac operon by repressor is referred to as negative control or regulation.

Gene regulation governing lactose operon of E.coli that involves the lac gene product is inducible because in this operon the addition of lactose itself stimulates the production of required enzymes.