Question

A permanent cure for ADA deficiency could be through:

• A. Bone marrow transplantation
• B. Modified lymphocyte transfusion
• C. Gene therapy at early embryonic stages
• D. Enzyme replacement therapy

Hint:

Remember that the first clinical gene therapy was given in 1990 to a 4-year-old girl with adenosine deaminase (ADA) deficiency.
Always distinguish between therapeutic modifications (which are temporary because somatic cells have a finite lifespan) and embryonic modifications (which are permanent because the gene is integrated during early development).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
This question belongs to Biotechnology, specifically the chapter "Biotechnology and its Applications" in the NCERT Class 12 curriculum, focusing on gene therapy.
We are asked to identify the technique that can provide a permanent cure for Adenosine Deaminase (ADA) deficiency.

Step 2: Key Concept or Approach:
ADA deficiency is a genetic disorder caused by the deletion or mutation of the gene coding for the enzyme adenosine deaminase, which is crucial for the functioning of the human immune system.
While bone marrow transplant and enzyme replacement can manage the disease, introducing the functional ADA gene into the stem cells at early embryonic stages is the only permanent cure.

Step 3: Detailed Explanation:

• ADA deficiency leads to Severe Combined Immunodeficiency (SCID) because T-lymphocytes fail to develop and function, leaving the patient extremely vulnerable to infections.

• Let us analyze the various treatment options:
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Enzyme replacement therapy: Active ADA enzyme is periodically injected into the patient. This is not a permanent cure as it requires lifelong repeated injections.
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Bone marrow transplantation: Healthy stem cells from a compatible donor are transplanted. This is also not fully permanent and carries risks of immunological rejection.
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Transfusion of genetically engineered lymphocytes: Lymphocytes are isolated from the patient's blood, grown in vitro, and a functional ADA cDNA is introduced using a retroviral vector. These modified cells are returned to the patient. Since lymphocytes are not immortal, the patient requires periodic infusions of these cells.
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Gene therapy at early embryonic stages: If the functional gene isolated from bone marrow cells producing ADA is introduced into cells at early embryonic stages, it integrates into the germline and stem cells permanently, providing a lifelong and complete cure.



Step 4: Final Answer:
The permanent cure for ADA deficiency is gene therapy at early embryonic stages, which is option (C).