AP Biologymediummcq1 pt
The trp operon's structural genes are transcribed when
A.tryptophan levels are low
B.tryptophan levels are high
C.lactose is present
D.glucose is absent only
Explanation
Core Concept
Low tryptophan leaves the repressor inactive, so RNA polymerase transcribes the biosynthesis genes. Rising product then represses them — feedback at the gene level.
Correct Answer
Atryptophan levels are low
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