Question: 154: 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) z, y, a genes will not be translated
(2) RNA polymerase will bind the promoter region
(3) Only z gene will get transcribed
(4) z, y, a genes will be transcribed
Answer: Option (1)
Explanation:
The i gene of the lac operon codes for the repressor protein.
Under normal conditions, the inducer lactose binds to the repressor and inactivates it.
This allows RNA polymerase to transcribe the structural genes z, y, a.
In the given case, the repressor produced by the mutated i gene cannot bind the inducer.
As a result, the repressor remains active and continues to bind to the operator region.
This prevents RNA polymerase from transcribing the structural genes.
Hence, even in the presence of lactose, the z, y, a genes are not expressed.
Therefore, the correct answer is that the z, y, a genes will not be translated.