試題詳解

39.The tryptophan operon of E.coli is repressed by tryptophan added to the growth medium. The tryptophan repr
(A) binds to RNA polymerase when tryptophan is present.
(B) binds to the trp operator in the absence of tryptophan.
(C) binds to the trp operator in the presence of tryptophan.
(D) is a DNA sequence.
(E) is an attenuator.