Question

type your response in the box.

imagine you are introducing the lac operon and the trp operon to students who have never learned about it before. complete the table to compare the similarities and differences between the two operons.

	trp operon	lac operon
environment
repressor protein
transcription

Explanation:

Compare operon types

• Trp operon: Repressible operon (normally active, turned off when tryptophan is abundant).
• Lac operon: Inducible operon (normally inactive, turned on when lactose is present and glucose is absent).

Compare environments and regulatory states

• Trp operon environment: Anabolic pathway (synthesizes tryptophan). Active when tryptophan levels are low; repressed when tryptophan levels are high.
• Lac operon environment: Catabolic pathway (breaks down lactose). Active when lactose is present and glucose is absent; repressed when lactose is absent.

Compare repressor proteins and transcription

• Trp repressor: Synthesized in an inactive form; requires tryptophan (corepressor) to bind to the operator and block transcription.
• Lac repressor: Synthesized in an active form; binds to the operator to block transcription until lactose (allolactose inducer) binds and inactivates it.

Answer:

Feature	Trp Operon	Lac Operon
Environment	Anabolic (tryptophan synthesis)	Catabolic (lactose breakdown)
Repressor protein	Synthesized inactive; activated by corepressor (tryptophan)	Synthesized active; inactivated by inducer (allolactose)
Transcription	On by default; turned off when tryptophan is high	Off by default; turned on when lactose is present