Trp operon: repressible vs. inducible
The trp operon is called repressible because:
Answer C: explanation for every choice
A
A molecule that removes the repressor describes an inducible operon, like lac.
B
Constant transcription describes a constitutive gene.
C
Correct. Tryptophan acts as a corepressor, turning the operon off when tryptophan is plentiful.
D
CAP activates operons such as lac. It does not repress trp.
TakeawayRepressible: the end product turns the operon off. Inducible: the substrate turns it on.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb40.