In E. coli, an operator gene combines with

Options

A. inducer gene to switch on structural gene action
B. inducer genet o switch off structural gene action
C. regulator protein (repressor) to switch off structural gene action
D. regulator protein to switch on gene action

Answer

To answer the question regarding what the operator gene in E. coli combines with, we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding the Components**:
- In E. coli, the genetic regulation involves several key components: operator genes, structural genes, repressor proteins, and inducers.

2. **Role of the Operator Gene**:
- The operator gene is a segment of DNA that acts as a regulatory switch for the structural genes. It controls the transcription of these genes.

3. **Combination with Repressor Protein**:
- The operator gene combines with a repressor protein. The repressor protein is produced by the regulator gene and binds to the operator.

4. **Effect of the Repressor-Operator Complex**:
- When the repressor protein is bound to the operator, it prevents RNA polymerase from transcribing the structural genes. This effectively "switches off" the expression of these genes.

5. **Inducers and Their Role**:
- Inducers can bind to the repressor protein, causing a conformational change that prevents the repressor from binding to the operator. This allows the structural genes to be expressed, effectively "switching on" their action.

6. **Conclusion**:
- Therefore, the operator gene combines with the repressor protein to switch off the action of the structural genes.

### Final Answer:
The operator gene in E. coli combines with the repressor protein to switch off structural gene action.

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