Adenosine deaminase (ADA) deficiency causes SCID primarily through accumulation of which toxic metabolite in lymphocytes?

• A Deoxyadenosine triphosphate (dATP) ✓
• B Inosine monophosphate (IMP)
• C Hypoxanthine
• D Xanthine

Explanation

ADA converts adenosine → inosine and deoxyadenosine → deoxyinosine. In ADA deficiency, deoxyadenosine accumulates and is phosphorylated to dATP, which reaches toxic concentrations preferentially in lymphocytes because of high deoxynucleoside kinase activity. Excess dATP inhibits ribonucleotide reductase, depletes other dNTP pools, inhibits DNA synthesis, and induces apoptosis, destroying T and B lymphocytes. Inosine, hypoxanthine, and xanthine are downstream products of adenosine catabolism that are not the primary toxic species in ADA-SCID.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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