Question

There is a mutation in the repressor that result in a molecule known as super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant? A- It cannot bind to operator B- It cannot bind to inducer C- It makes repressor bind to CRP D- It considers inactive repressor

Answer 1

B. It cannot bind to inducer.

Step-by-step explanation:

Normally in the cell, repressor binds to the operator and inhibit the transcription of lac operon genes. Activation of cellular lac operon will be occurred when inducer protein will bind to the repressor then repressor will not bind to the promoter because repressor will inactive and transcription of lac operon's genes will be initiated by binding of RNA polymerase to the promoter.

Now, if there will be mutation occurs in the repressor and in the result of that molecular becomes super-repressor and lac operon will be represses permanently, it means the inducer protein cannot bind to the repressor molecule and that's why repressor molecule will bind permanently to the promoter and inhibit the transcription of lac operon genes.