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Gene regulation governing lactose operon of E. coli that involves the lac I gene product is
A
Positive and inducible because it can be induced by lactose
B
Negative and inducible because repressor protein prevents transcription
C
Negative and repressible because repressor protein prevents transcription
D
Feedback inhibition because excess of β-galactosidase can switch off transcription
Detailed Solution
The repressor coded by the i gene binds the operator and prevents RNA polymerase from transcribing the operon (negative regulation).
Lactose (inducer) inactivates the repressor, allowing transcription — so the operon is inducible.
Lactose (inducer) inactivates the repressor, allowing transcription — so the operon is inducible.