Which biological structure inside human cells is the primary critical target of lethal ionizing radiation damage?
Answer and explanation
Correct answer: C. Nuclear DNA
- Step 1: Ionizing radiation generates hydroxyl radicals through radiolysis of intracellular water and directly ionizes biomolecules. Step 2. Unrepaired double-strand DNA breaks lead to chromosomal aberrations, mitotic catastrophe, and apoptotic cell death in rapidly dividing cancer cells. Answer: Nuclear DNA (causing double-strand chromosomal breaks). Why not the others: Ribosomes and ER are present in multiple copies and turnover rapidly; membrane lipid peroxidation contributes but is not the primary clonogenic lethal lesion.
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