The trp operon is a negative repressible operon that controls the biosynthesis of tryptophan. In a repressible operon, transcription is normally turned on and must be repressed. Repression is accomplished through the binding of tryptophan to the repressor, which renders the repressor active. The active repressor binds to the operator and prevents RNA polymerase from transcribing the structural genes.
-In the trp operon, what happens to the trp repressor in the absence of tryptophan?
A) It binds to the operator and represses transcription.
B) It cannot bind to the operator and transcription takes place.
C) It binds to the regulator gene and represses transcription.
D) It cannot bind to the regulator gene and transcription takes place.

Question

Quizplus · Accepted Answer

In the absence of tryptophan, the trp repressor is inactive and cannot bind to the operator, allowing transcription to occur.

The Trp Operon Is a Negative Repressible Operon That Controls