The first clinical gene therapy was given in 1990 to a 4 year old girl with adenosine deaminase (ADA) deficiency. This disorder is caused due to :-

Options

A. Deletion of the gene for adenosine deaminase
B. Inversion of the gene for adenosine deaminase
C. Duplication of the gene for adenosine deaminase
D. Translocation of gene for adenosine deaminase

Answer

To answer the question regarding the cause of adenosine deaminase (ADA) deficiency, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding ADA Deficiency**:
- Adenosine deaminase deficiency is a genetic disorder that affects the immune system, leading to severe combined immunodeficiency (SCID). It is crucial to understand that this condition arises from a problem with a specific gene.

2. **Identifying the Gene Involved**:
- The gene responsible for producing the enzyme adenosine deaminase is the ADA gene. This enzyme is essential for the proper functioning of lymphocytes, which are a type of white blood cell vital for the immune response.

3. **Analyzing the Genetic Mutations**:
- The question provides several options regarding what could cause ADA deficiency:
- Deletion of the gene for adenosine deaminase
- Inversion of the gene for adenosine deaminase
- Duplication of the gene for adenosine deaminase
- Translocation of the gene for adenosine deaminase

4. **Determining the Correct Cause**:
- Among these options, the most common cause of ADA deficiency is a deletion of the ADA gene. This deletion leads to the absence of the enzyme adenosine deaminase, resulting in the accumulation of toxic metabolites that harm lymphocytes.

5. **Conclusion**:
- Therefore, the correct answer to the question is that ADA deficiency is caused by the deletion of the gene for adenosine deaminase.

### Final Answer:
The disorder is caused due to **deletion of the gene for adenosine deaminase**.

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