Describe in brief :(a) What is germ line gene therapy? Why is it not encouraged?(b) Explain somatic cell gene therapy. Mention any two acquired disorders for which it is used.

Answer:

(a) Germ line gene therapy: the correct (normal) gene is introduced into the germ cells (sperm, egg) or the early embryo, so the change is passed on to the next generations. It is not encouraged because it permanently alters the human gene pool, its long-term effects on future generations are unknown and may be harmful, and it raises serious ethical problems (e.g. designer babies); hence it is banned or restricted in many countries.

(b) Somatic cell gene therapy: the normal gene is introduced into the somatic (body) cells of the patient, e.g. bone marrow cells or lymphocytes, usually using a vector such as a retrovirus. The cells are corrected and returned to the patient (ex vivo) or the gene is delivered directly (in vivo). The effect is limited to the treated person and is not inherited. Example: treatment of ADA (adenosine deaminase) deficiency (SCID). Acquired disorders treated: cancer and AIDS (also some infectious and cardiovascular diseases).