Explanation

A functional ADA CDNA can be introduced into cells of the patients receiving gene therapy by using vector constituted by retrovirus. The SCID patient has a defective gene for the enzyme Adenosine Deaminase (ADA). He/she lacks functional T-lymphocytes and, therefore fails to fight the infecting pathogen. Lymphocytes are extracted from the patient’s bone marrow and a normal functional copy of human gene coding for ADA is introduced into these lymphocytes with the help of retrovirus