McGraw-Hill Online Learning Center Test<BLURT>

McGraw-Hill Online Learning Center Test


1. Review the animation and answer the following questions.

Operons such as the E. coli trp operon make use of repressible enzymes. They are called repressible because

A. the activity of each of the enzymes can be repressed by tryptophan.
B. the presence of tryptophan inhibits their production.
C. a repressor is required for their production.
D. they are only produced in the presence of the substance they act upon.


2. Binding of the repressor to the operator region A. prevents binding of RNA polymerase.
B. prevents initiation of translation.
C. allows transcription to begin.
D. does not affect transcription.


3. Tryptophan acts as a corepressor because it A. inhibits the activity of the first enzyme in the pathway.
B. binds directly to the operator site.
C. binds to an inactive repressor making it active.
D. binds to the promoter preventing RNA polymerase from binding.
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