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

1. Negative and inducible because repressor protein prevents transcription
2. Negative and repressible because repressor protein prevents transcription
3. Feedback inhibition because excess of β-galactosidase can switch off transcription
4. Positive and inducible because it can be induced by lactose

Correct answer: Negative and inducible because repressor protein prevents transcription

Solution

The lac operon is under negative control because the lacI gene produces a repressor that blocks transcription when lactose is absent. It is inducible because the presence of lactose (actually allolactose) inactivates the repressor, allowing transcription to proceed.

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