Assertion: The inactivation of any vector gene due to insertion of desired gene called as insertional inactivation
Reason :Some time restriction sites are also present in between the gene sequence of vector

Options

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

Answer

### Step-by-Step Text Solution:

1. **Understanding the Assertion**:
- The assertion states that "the inactivation of any vector gene due to the insertion of a desired gene is called insertional inactivation."
- This means that when a foreign gene is inserted into a vector (like a plasmid), it disrupts the function of the original gene present in the vector.

2. **Understanding the Reason**:
- The reason provided is that "sometimes restriction sites are also present in between the gene sequence of the vector."
- Restriction sites are specific sequences in the DNA where restriction enzymes can cut the DNA. This is crucial for inserting the desired gene into the vector.

3. **Connecting Assertion and Reason**:
- The assertion and reason are connected because the presence of restriction sites allows for the insertion of the desired gene into the vector.
- When the desired gene is inserted at a restriction site, it can lead to the inactivation of the original gene in the vector, which is the essence of insertional inactivation.

4. **Example to Illustrate**:
- Consider the plasmid PBR322, which has genes for tetracycline and ampicillin resistance.
- If a desired gene is inserted into the tetracycline resistance gene, the original tetracycline resistance gene becomes inactive, demonstrating insertional inactivation.

5. **Conclusion**:
- Both the assertion and the reason are true, and the reason correctly explains the assertion.
- Therefore, the correct option is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.