(a) Mention the cause and the body system affected by ADA deficiency in humans. (b) Name the vector used for transferring ADA-DNA into the recipient cells in humans. Name the recipient cells.

(a) ADA deficiency is caused by mutation in ADA gene that code for Adenosine deaminase enzyme involved in purine metabolism. it affects immune response and causes SCID (severe combined immunodeficiency) (b) The ex vivo introduction of functional ADA gene in bone marrow cells of the patient, suffering with SCID, is done through an engineered retrovirus containing a functional ADA gene. Recipient cells are lymphocytes/bone marrow cells.