In inducible operon, regulatory gene synthesize:

Options

A. Promoter
B. Operator
C. Repressor
D. Aporepressor

Answer

To solve the question regarding what regulatory genes synthesize in an inducible operon, we can break down the information step by step.

### Step-by-Step Solution:

1. **Understanding Inducible Operons**:
- Inducible operons are a type of operon that is usually off but can be turned on (induced) in the presence of a specific substrate or signal.

2. **Role of Regulatory Genes**:
- Regulatory genes are responsible for controlling the expression of the operon. They produce proteins that can either activate or repress the transcription of downstream genes.

3. **Identifying the Products of Regulatory Genes**:
- In the context of an inducible operon, the regulatory gene synthesizes a specific protein that plays a crucial role in controlling the operon.

4. **Understanding the Function of the Synthesized Protein**:
- The protein produced by the regulatory gene in an inducible operon is known as a repressor. This repressor can bind to the operator region of the operon.

5. **Mechanism of Action**:
- When the repressor binds to the operator, it prevents RNA polymerase from transcribing the downstream genes, effectively blocking protein synthesis until the repressor is removed (induced).

6. **Conclusion**:
- Therefore, in an inducible operon, the regulatory gene synthesizes a repressor, which is crucial for controlling the operon’s activity.

### Final Answer:
The correct answer is **C) repressor**.