This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2019, Subject name: Microbiology
Gene not involved in SCID 
Select and explain. 
A. BTK, B. ZAP70, C. IL2RG, D. JAK3
A: BTK
Answer: A: BTK 
Explanation: BTK gene is involved in Buon's disease or X linked agammaglobulinemia. Most cases of X linked Severe combined immunodeficiency (SCID) are due to mutations in IL2RG gene. Other mutations are defective enzyme production in Adenosine deaminase and mutations in ZAP -70 which causes defective T cell signalling which causes combined immunodeficiency and mutation occurs in JAK-3.