Which of the following could be a premanent cure for treatment of severe combined immunodeficiency (SCID)?

Options

A. Bone marrow transplantation
B. Enzyme replacment therapy
C. Both (1) and (2)
D. Gene therapy

Answer

### Step-by-Step Solution:

1. **Understanding SCID**: Severe Combined Immunodeficiency (SCID) is a genetic disorder characterized by a deficiency in both T and B lymphocyte systems, leading to a severely compromised immune system.

2. **Identifying the Cause**: The primary cause of SCID is a mutation in the ADA gene (adenosine deaminase gene), which is crucial for the immune system's function.

3. **Mechanism of the ADA Gene**: The ADA gene encodes the enzyme adenosine deaminase. A mutation in this gene results in a lack of functional enzyme, which is essential for the breakdown of toxic metabolites that can accumulate and harm lymphocytes.

4. **Gene Therapy as a Treatment**: Gene therapy involves introducing a normal, functional copy of the ADA gene into the patient's cells. This is typically done using a retrovirus that carries the healthy gene.

5. **Procedure**: The retrovirus containing the functional ADA gene is injected into the patient's bone marrow cells (ex vivo). These cells are then modified to incorporate the healthy gene.

6. **Integration into Host Cells**: The introduced gene can either integrate into the host's chromosomes at various sites or replace the defective gene, allowing for the production of the functional enzyme.

7. **Permanent Cure**: Unlike other treatments such as bone marrow transplantation or enzyme replacement therapy, which are temporary and require ongoing treatment, gene therapy aims to provide a permanent solution by correcting the underlying genetic defect.

8. **Conclusion**: Therefore, gene therapy is considered a permanent cure for SCID, as it addresses the root cause of the disorder by correcting the genetic mutation.

### Final Answer:
The permanent cure for the treatment of severe combined immunodeficiency (SCID) is **gene therapy**.

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