Which of the following molecules, when taken up by the cell, binds to the repressor allowing...

Which of the following molecules, when taken up by the cell, binds to the repressor allowing it to bind to the operator?

-Inducer

-Corepressor

-Repressor

-Promoter

Expert Solution

Operon is smallest regulatory unit which consists of regulatory gene, promoter, operator and structural genes.

Regulatory gene can produce activator or repressor. If the activator is produced by reguloty gene, binding of activator near the promoter site increase the rate of transcription, type of regulation is known as positive regulation. If a repressor is produced by regulatory gene binding of the repressor to the operator lead to decrease in rate of transpiration. Such type of regulation is known as negative regulation. As in the question repressor is present so it is a negative control operon.

Negative control operons can be inducible operon or repressible operon. In negative control inducible operon. Repressor alone can bind to operator gene and stop transcription. But in presence of inducer, repressor become inactive and doesnot bind to operator gene, so RNA polymerase bind to promoter, move to structural gene and transcription oocurs.

In negative control repressible operon, repressor (inactive) alone cannot bind to operator, so transcription occurs. When a corepressor is present it bind to repressor and become active repressor that bind to operator and block path of RNA polymerase leading to stop of transcription.

In the question, inducer cannot be right option because binding of inducer make repressor inactive and then it cannot bind to operator. Only when repressor (inactive) bind to corepressor, it becomes active and bind to operator and stop transcription so corepressor is right choice of this question.

Promoter cannot bind to repressor. Promoter is a gene on which RNA polymerase binds. So this is also wrong option. Repressor doesnot bind with itself to become active only binding of corepressor make repressor active for binding to operator.

So only corepressor is right choice of this question.

The process occuring is shown in figure below

gladiator answered 1 year ago

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