Which of the following statements is incorrect about gene therapy in ADA deficiency ?

Options

A. Lymphocytes from patient's blood are taken out and cultured
B. A functional ADA-cDNA is introduced into these lymphocytes
C. Lymphocytes are then introduced in the body of patient
D. Patient does not require periodic infustion of genetically engineered lymphocytes

Explanation

To determine which statement is incorrect about gene therapy in ADA (adenosine deaminase) deficiency, we can follow these steps:

### Step-by-Step Solution:

1. **Understand ADA Deficiency**:
- ADA deficiency is a genetic disorder that leads to severe combined immunodeficiency (SCID). This condition is caused by a lack of the enzyme adenosine deaminase, which is crucial for the immune system.

2. **Know the Basics of Gene Therapy**:
- Gene therapy aims to treat or cure genetic disorders by introducing a functional copy of a gene into a patient's cells. In the case of ADA deficiency, this involves using gene therapy to provide the body with the missing ADA enzyme.

3. **Process of Gene Therapy for ADA Deficiency**:
- Lymphocytes (a type of white blood cell) are extracted from the patient's blood.
- These lymphocytes are cultured in a laboratory setting.
- A functional copy of the ADA gene (in the form of complementary DNA, cDNA) is introduced into these lymphocytes using a retroviral vector.
- After the lymphocytes are genetically modified, they are reintroduced into the patient's body.

4. **Evaluate the Statements**:
- **Statement 1**: Lymphocytes are taken from the patient, cultured, and a functional ADA cDNA is introduced. This is correct.
- **Statement 2**: Lymphocytes are then introduced back into the patient. This is also correct.
- **Statement 3**: The patient does not require periodic infusion of genetically engineered lymphocytes. This statement is incorrect because the modified lymphocytes are not immortal, and the patient does require periodic infusions to maintain the necessary enzyme levels.
- **Statement 4**: The patient requires periodic infusion of genetically engineered lymphocytes. This is correct.

5. **Identify the Incorrect Statement**:
- The incorrect statement is the one that claims the patient does not require periodic infusions of genetically engineered lymphocytes. Therefore, the answer is that this statement is incorrect.

### Conclusion:
The incorrect statement about gene therapy in ADA deficiency is that the patient does not require periodic infusion of genetically engineered lymphocytes.

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