Question

An example of gene therapy is
A. Production of injectable Hepatitis-B vaccine
B. Production of vaccines in food crops like potatoes which can be eaten
C. Introduction of gene for adenosine deaminase in persons suffering from severe combined immuno-deficiency (SCID)
D. Production of test tube babies by artificial insemination and implantation of fertilized egg

Answer 1

Hint:-Gene therapy, also termed as gene transfer therapy, includes the introduction of a wild type gene into the genome of a diseased individual, caused by mutation of that particular gene. Thus, the inserted wild type gene integrates with the specific chromosome at specific sites and starts producing the required gene product.

Complete answer:
Gene therapy is used to treat people with genetic disorders or diseases that are caused by genetic defects. For example – in SCID, a gene called the ADA gene, which codes for the enzyme adenosine deaminase is mutated. To repair this effect, a retrovirus containing a functional wild-type ADA gene is inserted into the patient’s bone marrow ex vivo and again incorporated in the patient's bone marrow. The gene inserted either integrates into the chromosome of the host at several sites away from the mutated DNA or replaces the faulty gene and produces functional enzymes.
On the other hand, the production of vaccines is a gene manipulation technique. A vaccine is a preparation containing killed or inactivated microorganisms or its toxic components and exerts immunologic response to an individual. It acts as an immune booster and produces memory B cells. Eg. – Hepatitis B vaccine, vaccines for crops, etc. The production of test-tube babies refers to a process in which an ovum is fertilized externally outside the body by in vivo fertilization procedures.
Thus, the right option is C.

Note:- Gene therapy is the revolutionary success of recombinant DNA technology. In the late 20th century, a group of scientists discovered a few techniques in which the DNA of an organism, coding for a particular protein can be transferred and recombined to the DNA of a different organism. This recombination results in the expression of that gene product in the host organism.