What is the term used for the treatment of a genetic disorder by alte…

The correct answer is Option (1) → Gene therapy

Some diseases are caused by a defective gene. Gene therapy is a collection of methods that corrects such a gene defect: a normal gene is delivered into the person’s cells to take over the work of the non-functional gene. The first clinical gene therapy was given in 1990 to a 4-year-old girl with adenosine deaminase (ADA) deficiency.

Option (1) Gene therapy — Correct. Gene therapy treats a hereditary disease by inserting genes into a person’s cells and tissues. It acts on the cause, the faulty gene itself.

Option (2) rDNA technology — Incorrect. rDNA (recombinant DNA) technology is the general method of joining DNA from different sources and making it multiply in a host. Gene therapy uses its tools, but the term does not name the treatment of a disorder.

Option (3) Bone marrow transplantation — Incorrect. Bone marrow transplantation can cure ADA deficiency in some children, but it replaces cells, not genes. The book notes that it is not completely curative.

Option (4) Enzyme replacement therapy — Incorrect. In enzyme replacement therapy, functional ADA is injected into the patient. The defective gene stays as it is, so the treatment has to be repeated.

NCERT Extract:
Gene Therapy – “… 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. Correction of a genetic defect involves delivery of a normal gene into the individual or embryo to take over the function of and compensate for the non-functional gene.”
Gene Therapy – “… In some children ADA deficiency can be cured by bone marrow transplantation; in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches that they are not completely curative.”