The tryptophan operon in some bacteria is a repressible operon.Which of the following statements correctly describes this operon?
A)It is permanently active.
B)It is activated only when tryptophan is present in the growth medium.
C)It is activated only when glucose is present in the growth medium.
D)It is deactivated whenever tryptophan is added to the growth medium.

Question

Quizplus · Accepted Answer

The tryptophan operon is a repressible operon, which means it is normally active but can be turned off or repressed when a specific molecule (in this case, tryptophan) is present in the growth medium. When tryptophan is added to the medium, it binds to the repressor protein and activates it, causing the repressor to bind to the operator region of the operon and prevent RNA polymerase from transcribing the genes. Therefore, statement D is correct: the tryptophan operon is deactivated whenever tryptophan is added to the growth medium.

The Tryptophan Operon in Some Bacteria Is a Repressible Operon