Hydroxyl radical (OH.), the most reactive oxygen species, causes oxidative damage to DNA. Which specific DNA base modification is the hallmark of hydroxyl radical attack and is commonly measured as a biomarker of oxidative DNA damage?
- A Thymine dimer formation
- B Deamination of cytosine to uracil
- C 8-hydroxydeoxyguanosine (8-OHdG) ✓
- D Methylation of adenine at the N6 position
Correct answer: C. 8-hydroxydeoxyguanosine (8-OHdG)
Explanation
Hydroxyl radicals attack guanine at the B8 position to form 8-hydroxydeoxyguanosine (8-OHdG), the most widely used biomarker of oxidative DNA damage. Thymine dimers are caused by UV radiation, not free radicals. Deamination of cytosine is spontaneous or nitrous acid-induced. N6-methylation of adenine is an epigenetic modification, not oxidative damage.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.