What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency?
Gene Therapy. It is defined as the introduction of a normal functional gene into cells that contain the defective allele of the concerned gene with the objective of correcting a genetic disorder or an acquired disorder. Treatment of ADA deficiency: Gene therapy was used to correct the genetic disorder called Severe Combined Immunodeficiency (SCID) syndrome produced by adenosine deaminase (ADA) deficiency. In this, Normal ADA gene copies were produced by cloning. Packed into a retrovirus, most of the viral genes were replaced by the ADA gene. Lymphocytes were isolated from the patients. Recombinant DNA of the recombinant retroviruses was used to infect the lymphocytes. The infected cells expressing the ADA gene were injected back into the patients. The normal ADA gene was then expressed in the patients and ADA deficiency is partially corrected. If the gene isolated from bone marrow cells producing ADA is introduced into embryonic cells at early stages, it could provide a permanent cure.
