The functional ADA cDNA can be introduced into the cells of the patient receiving gene therapy by using a vector consituted by :

Options

A. E.coil
B. Reovirus
C. Retrovirus
D. Agrobacterium

Answer

To solve the question regarding which vector can be used to introduce functional ADA cDNA into the cells of a patient receiving gene therapy, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: The question refers to introducing functional ADA (adenosine deaminase) cDNA into cells for gene therapy. ADA deficiency leads to severe combined immunodeficiency (SCID), which affects lymphocyte proliferation.

2. **Identify the Options**: The options provided are:
- E. coli
- Rheovirus
- Retrovirus
- Agrobacterium

3. **Analyze Each Option**:
- **E. coli**: This bacterium is often used in molecular biology as a host for cloning and expressing genes. It can be used to produce cDNA clones that encode the ADA gene sequences.
- **Rheovirus**: This is a virus that can infect mammalian cells but is not commonly used for gene therapy involving ADA cDNA.
- **Retrovirus**: This type of virus is indeed used in gene therapy because it can integrate into the host genome, but the question specifically asks for a vector constituted by a particular organism.
- **Agrobacterium**: This bacterium is primarily used in plant biotechnology for creating transgenic plants, not for human gene therapy.

4. **Select the Correct Answer**: Based on the analysis, E. coli is the most suitable choice as it is used to clone and express the ADA cDNA for therapeutic purposes.

5. **Conclusion**: The functional ADA cDNA can be introduced into the cells of the patient receiving gene therapy by using a vector constituted by **E. coli**.

### Final Answer:
The correct option is **E. coli**.

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