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The trp repressor blocks transcription of the trp operon when the repressor binds to tryptophan
Explanation:
Trp operon is found in bacteria like E Coli. The operon is used to biosynthesize tryptophan when it is not readily available in the environment.
The transcription of the genes of the operon is regulated by a repressor that binds to the operator of the operon blocking off RNA polymerase from binding on its promoter. This occurs when the repressor is activated by the binding of a tryptophan molecule to the repressor changing its conformation and enabling it to bind the operator.
When there is very little tryptophan, the repressor is rarely bound by tryptophan hence tending to be inactive as a corepressor. It does not bind its operator region on the operon allowing the genes to be transcribed by RNA polymerase.
Learn More:
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