Question

When tryptophan is present:

पर्याय

• repressor is unable to bind to the operator.

• transcription of structural genes occurs.

• repressor is able to bind to the operator.

• both repressor are unable to bind to the operator and transcription of structural genes occurs.

Answer 1

repressor is able to bind to the operator.

Explanation:

The trp operon is a repressible system in bacteria that is usually “on” but can be turned “off” when tryptophan is abundant. Unlike the lac operon, where the substrate (lactose) turns the system on, in this case, tryptophan acts as a co-repressor. When tryptophan is present, it binds to the inactive repressor protein, changing its shape so that it becomes active and can bind to the operator. Once bound, the repressor physically blocks RNA polymerase from moving forward, which stops the transcription of structural genes to prevent the cell from wasting energy making an amino acid it already has