Assertion :- The activity of RNA polymerase at a promotor is
regulated by interaction with accessory protein, which affect its
ability to recognize start sites.
Reason : The accessibility of promotor region of prokaryotic DNA is
in many cases is regulated by interaction of proteins with operators.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are trur but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is Flase.
D. If both Assertion & Reason are false.

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Assertion:**
- The assertion states that the activity of RNA polymerase at a promoter is regulated by accessory proteins. These proteins influence how well RNA polymerase can recognize the start sites for transcription.
- RNA polymerase is crucial for transcription, as it synthesizes RNA from a DNA template.

2. **Understanding the Reason:**
- The reason provided explains that in prokaryotic DNA, the accessibility of the promoter region is often controlled by the interaction of proteins with operators.
- Operators are segments of DNA that regulatory proteins can bind to, affecting the transcription process.

3. **Analyzing the Assertion:**
- The assertion is correct because RNA polymerase does require accessory proteins, like sigma factors, to initiate transcription effectively. These proteins help RNA polymerase to recognize and bind to the promoter region.

4. **Analyzing the Reason:**
- The reason is also correct. In prokaryotes, the binding of repressor proteins to operators can block RNA polymerase from accessing the promoter, while inducer proteins can facilitate this access, thereby regulating transcription.

5. **Determining the Relationship:**
- While both the assertion and reason are true, the reason does not directly explain the assertion. The assertion focuses on RNA polymerase and accessory proteins, while the reason discusses the role of operators in regulating promoter accessibility.

6. **Conclusion:**
- Therefore, the correct answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

**Final Answer:**
Both assertion and reason are true, but reason is not the correct explanation of the assertion (Option B).

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