NEET 2015 Biology question

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

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

Answer: (1)

Solution

The *lac I* (regulator) gene codes for the repressor protein, which binds to the operator and blocks RNA polymerase, so transcription of the structural genes (*z*, *y*, *a*) is prevented. This is negative regulation. In the presence of the inducer (lactose/allolactose) the inducer binds the repressor, which leaves the

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Question ID VK-091738