Question

SCID is caused by defective gene coding for the enzyme

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

Answer 1

The correct option is C Adenosine deaminase

SCID or severe combined immunodeficiency is a primary immune deficiency. It is a genetic disorder characterized by the inhibition of development of functional B cells and T cells, caused by numerous genetic mutations. The gene coding for adenosine deaminase (ADA) which is necessary for the breakdown of purines get mutated and this defective now not able encode ADA. Lack of ADA causes accumulation of dATP that reduces ribonucleotides to generate deoxyribonucleotides. Without functional ribonucleotide reductase, lymphocyte proliferation is inhibited and such disorder is called as SCID. Thus, the correct answer is option C.