True or false: inducible negative regulation occurs when the gene is not transcribed in the presence of a specific small molecule?

Question

BlackTom AI · Accepted Answer

Inducible negative regulation is characterized by a repressor protein that blocks transcription until a specific small molecule (an inducer) binds the repressor and disables it, allowing transcription to proceed.

1) Relevant concepts:
- Negative regulation = transcription is controlled by a repressor that binds the operator to block RNA polymerase.
- Inducible system = transcription is off in the absence of the small molecule and turned on when the small molecule (inducer) is present.
- Classic example: the lac operon. LacI repressor binds the operator and prevents transcription; when the inducer allolactose (derived from lactose) binds LacI, the repressor releases and transcription is induced.

2) Step-by-step reasoning:
- The statement claims: “inducible negative regulation occurs when the gene is not transcribed in the presence of a specific small molecule.”
- In an inducible negative system, the baseline (no inducer) state is repression: gene not transcribed.
- When the small molecule (inducer) is present, it binds the repressor and prevents operator binding, so transcription occurs.
- Therefore the presence of the small molecule leads to transcription, not to continued absence of transcription.

3) Calculations: none required; logical steps above fully trace the mechanism.

4) Why the correct answer is correct:
- Because inducible negative regulation specifically describes a mechanism where the small molecule relieves repression (induces transcription). The statement reverses this relationship, so it is incorrect.

5) Why the other option is incorrect:
- “True” would assert that transcription is OFF when the inducer is present — this contradicts the definition and examples (e.g., lac operon), so it is incorrect.

Conclusion: The correct response is False, which matches the provided answer.

True or false: inducible negative regulation occurs when the gene is not transcribed in the presence of a specific small molecule?判断题

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