Injecting functional adenosine deaminase into a patients (lacking ADA gene) blood cells may be considered as

Options

A. Gene therapy
B. Enzyme replacement therapy
C. Both (1) & (2)
D. Genetic engineering

Answer

### Step-by-Step Solution:

1. **Understanding the Condition**: The question involves a patient who lacks the ADA (adenosine deaminase) gene. This deficiency leads to a condition known as severe combined immunodeficiency syndrome (SCID), which affects the maturation of lymphocytes, crucial for the immune response.

2. **Role of Adenosine Deaminase**: Adenosine deaminase is an enzyme that is essential for the proper functioning and maturation of lymphocytes. Without this enzyme, the patient cannot effectively produce mature lymphocytes, leading to a compromised immune system.

3. **Therapeutic Approaches**: There are several therapeutic strategies for treating ADA deficiency:
- **Enzyme Replacement Therapy**: This involves administering functional ADA enzyme from an external source to temporarily alleviate the symptoms.
- **Lymphocytic Infusion**: This is a temporary measure where healthy lymphocytes are infused into the patient.
- **Bone Marrow Transplantation**: This method involves transplanting healthy bone marrow cells that can produce the necessary enzymes and cells.
- **Gene Therapy**: This is a more permanent solution where the functional gene is introduced into the patient's cells to enable them to produce their own ADA enzyme.

4. **Identifying the Correct Therapy**: The question specifically mentions "injecting functional adenosine deaminase into a patient's blood cells." This indicates that the therapy being referred to is not a permanent solution like gene therapy, but rather a temporary measure to provide the enzyme that the patient lacks.

5. **Conclusion**: Therefore, the correct answer to the question is that injecting functional adenosine deaminase into a patient's blood cells is considered **Enzyme Replacement Therapy**.