A: Operator gene is functional when it is not blocked by repressor.
R: Regulator gene produces active protein only which acts on operon system in E.coil.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark
B. If both Assertion & Reason are true and the reason is not the correct explanation of the assertion , then mark
C. If Assertion is ture statement but Reason is false, then mark.
D. If both Assertion and Reason are false statements, then mark.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the operator gene is functional when it is not blocked by a repressor. This means that the operator can carry out its role in transcription when the repressor is absent.

2. **Understanding the Reason**:
- The reason states that the regulator gene produces an active protein that acts on the operon system in E. coli. This implies that the regulator gene plays a crucial role in controlling the operon by producing proteins that can either activate or inhibit transcription.

3. **Explaining the Operon System**:
- In E. coli, the operon system consists of structural genes, an operator, and a promoter. The operator is a specific DNA sequence where regulatory proteins (like repressors) bind to control the transcription of the structural genes.

4. **Role of the Repressor**:
- When the repressor protein binds to the operator, it inhibits the binding of RNA polymerase, thereby preventing transcription of the structural genes. Thus, the operator is not functional when the repressor is bound.

5. **Function of the Regulator Gene**:
- The regulator gene, located near the operon, produces the repressor protein. This protein can bind to the operator and block transcription. When the regulator gene is active, it produces the repressor, which affects the operon system.

6. **Conclusion**:
- Both the assertion and the reason are correct. The assertion correctly states that the operator gene is functional when not blocked by the repressor, and the reason accurately describes the role of the regulator gene in producing the repressor protein that acts on the operon system in E. coli.

7. **Final Answer**:
- Both the assertion and reason are true, and the reason correctly explains the assertion. Therefore, the correct option is option 1: "Assertion and reason both are true, and reason is the correct explanation of assertion."