Question

SCID is caused by defective gene coding for enzyme

• A. Adenosine transaminase
• B. Adenosine deaminase
• C. Adenosine deaminase
• D. Adenosine transferase

Answer 1

The correct option is B Adenosine deaminase

SCID
Severe Combined ImmunoDeficiency Syndrome (SCID) is a disorder caused by a mutation in the gene encoding the enzyme adenosine deaminase (ADA). Lack of ADA gene results in depletion of T-lymphocytes and it affects the activation of B cells as well.

Adenosine deaminase
Adenosine deaminase (ADA) is an enzyme that converts deoxyadenosine to deoxyinosine, the latter being less toxic for the lymphocytes. ADA enzyme is abundantly present in lymphocytes. Absence or deficiency of ADA leads to accumulation of toxic deoxyadenosine. This inturn results in SCID.

Final answer:
(d) Adenosine deaminase