Gene Therapy and ADA Deficiency — NEET Biology

Correct answer: A — Only S3 and S5 are not correct

The core concept is gene therapy, its definition, the ADA deficiency example, and the limitations of various treatments as described in NCERT. S1: Correct. NCERT states, 'Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo. Here genes are inserted into a person’s cells and tissues to treat a disease.' S2: Correct. NCERT states, 'The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency.' S3: Incorrect. NCERT states, 'However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes.' It also states, 'However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.' The statement incorrectly combines these two facts, implying periodic infusion provides a permanent cure *if* introduced at early embryonic stages, which is not what NCERT states. Periodic infusion is required *because* the cells are not immortal, while early embryonic introduction is a separate approach for a *potential permanent cure*. S4: Correct. NCERT states, 'A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient.' S5: Incorrect. NCERT states regarding bone marrow transplantation and enzyme replacement therapy for ADA deficiency: 'But the problem with both of these approaches that they are not completely curative.' Therefore, they are not completely curative or permanent solutions. Thus, statements S3 and S5 are NOT correct.