Q.ADA is an enzyme which is deficient in a genetic disorder SCID. What is the full form of ADA?

ADA stands for Adenosine deaminase, an enzyme crucial for the functioning of the immune system. In its absence, a genetic disorder called SCID (Severe Combined Immunodeficiency) develops, where lymphocytes fail to mature and the body cannot mount an immune response.

The enzyme catalyzes the breakdown of adenosine and deoxyadenosine, which would otherwise accumulate to toxic levels in lymphocytes. Without functional ADA, these cells die, leaving patients extremely vulnerable to infections. …

The question connects a critical enzyme to one of the most well-known genetic disorders treated through gene therapy. SCID, or Severe Combined Immunodeficiency, is a group of inherited disorders that severely compromise the immune system, leaving affected individuals vulnerable to repeated and life-threatening infections. Among the various forms of SCID, one particular type arises from a deficiency of the enzyme ADA.

Adenosine deaminase is an enzyme involved in purine metabolism—the biochemical pathway that breaks down purine nucleotides. When ADA is absent or deficient, toxic metabolites accumulate in the body, particularly affecting lymphocytes (the white blood cells crucial for immune function). The buildup of these toxic substances, especially deoxyadenosine, is lethal to T-cells and B-cells, which are the backbone of the adaptive immune response. Without functional lymphocytes, children born with ADA deficiency have virtually no immune defense.

Method — expand each syllable of the acronym

A-D-A = Adenosine + Deaminase.

"Adenosine" is the substrate (a nucleoside), "deaminase" names the enzyme's action (removing an amine group). …