Biotechnological Applications In Medicine

In the gene therapy for adenosine deaminase deficiency, functional ADA genes were introduced into the patient's lymphocytes, which were then returned to the body; however, because these mature lymphocytes are not immortal and have a limited lifespan, the procedure must be repeated periodically, as noted in NCERT Class 12, Chapter 11 (Biotechnology and its Applications). A permanent cure would require introducing the correct gene into the precursor or stem cells of bone marrow at an early stage of life, so that all subsequent blood cells carry the functional gene. The idea that the gene mutates within hours is biologically incorrect and is not the reason given in the text. The enzyme adenosine deaminase does not degrade the viral vector, so that explanation is invalid. The patient developing immunity specifically against the gene itself is not the stated cause of the temporary effect. This limitation highlights the broader distinction between somatic gene therapy, which corrects body cells temporarily, and the more lasting correction that targeting early stem cells could in principle provide. A biological consistency check supports the answer: since the corrected cells are short-lived and continually replaced by uncorrected cells, repeated treatment is needed to maintain the therapeutic benefit.