Question: why is trp operon repressible?
Answer: The Tryptophan Operon – A Repressible Operon System. The tryptophan (trp) operon system is a type of repressible operon system. ... When tryptophan is present, it binds the trp repressor and induces a conformational change in that protein, enabling it to bind the trp operator and prevent transcription (operon is repressed) ...