Assertion: In gene therapy of SCID, a patient requires periodic infusion of genetically engineered lymphocytes
Reason :If the ADA gene is introducted into cells at early embryonic stage, it could be a permanent cure

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 Solution:

1. **Understanding the Assertion**:
- The assertion states that in gene therapy for Severe Combined Immunodeficiency Disease (SCID), patients need periodic infusions of genetically engineered lymphocytes.
- This is true because SCID is caused by a deficiency in the enzyme adenosine deaminase (ADA), which is crucial for the immune system's function. Patients with SCID often receive engineered lymphocytes to help manage their condition.

2. **Understanding the Reason**:
- The reason provided states that if the ADA gene is introduced into cells at the early embryonic stage, it could lead to a permanent cure.
- This is also true because introducing the ADA gene at the embryonic stage allows for the normal gene to be incorporated into all cells as they divide, potentially curing the deficiency permanently.

3. **Evaluating the Relationship**:
- While both statements are true, the reason does not directly explain the assertion. The assertion discusses the need for periodic infusions due to the current limitations of gene therapy, while the reason discusses a potential permanent solution that could be achieved if the gene therapy is performed at an embryonic stage.

4. **Conclusion**:
- Therefore, both the assertion and reason are true, but the reason is not a correct explanation of the assertion. The correct answer is option B: Both assertion and reason are true, but the reason is not a correct explanation of the assertion.