In negative operon

Options

A. Inducer binds with repressor
B. Co-repressor does not binds with repressor
C. Corepressor binds with inducer
D. CAMP have negative effect on lac operon

Answer

### Step-by-Step Solution:

1. **Understanding Negative Operon**:
- A negative operon is a type of operon that is regulated by a repressor protein. In this system, the repressor binds to the operator region of the operon, preventing transcription of the genes.

2. **Identifying the Inducer**:
- In the context of the lac operon, the inducer is lactose. When lactose is present, it acts as an inducer by binding to the repressor protein.

3. **Repressor and Inducer Interaction**:
- When lactose binds to the repressor, it causes a conformational change in the repressor protein. This change prevents the repressor from binding to the operator region of the operon.

4. **Effect on Gene Expression**:
- With the repressor unable to bind to the operator, RNA polymerase can access the promoter region, allowing transcription of the genes involved in lactose metabolism to occur.

5. **Evaluating the Options**:
- Option A states that "inducer binds with repressor," which is correct as it describes the interaction that leads to the activation of the operon.
- Option B states that "co-repressor does not bind with repressor," which is not relevant to the lac operon.
- Option C states that "co-repressor binds with inducer," which is incorrect in the context of the lac operon.
- Option D states that "CAMP has side effects on lac operon," which is misleading as cAMP is involved in the regulation but not as a direct negative control.

6. **Conclusion**:
- The correct answer is **Option A: Inducer binds with repressor**.