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NEET 2022, Biology Q74: Gene Regulation and Genetic Code

NEET2022Biology
Q.

In an E. coli strain i gene gets mutated and its product can not bind the inducer molecule. If growth medium is provided with lactose, what will be the outcome ?

  1. A

    Only z gene will get transcribed

  2. B

    z, y, a genes will be transcribed

  3. C

    z, y, a genes will not be translated

  4. D

    RNA polymerase will bind the promoter region

Solution

In the lac operon, the i gene encodes the repressor protein. Lactose acts as an inducer that binds the repressor and inactivates it, allowing transcription of the structural genes z, y, a.

If the mutant repressor cannot bind the inducer, it remains active and continues to occupy the operator, even when lactose is present. RNA polymerase cannot transcribe the structural genes, so the z, y, a genes will not be transcribed and consequently will not be translated.

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