Practice question

Cellular respiration generates reactive oxygen species that oxidize guanine at C8 forming 8-oxo-7,8-dihydroguanine, highly mutagenic lesion due to altered glycosidic bond preference. In syn conformation, 8-oxoG pairs with adenine instead of cytosine, causing G:C to T:A transversion after replication if not corrected. OGG1 DNA glycosylase excises 8-oxoG paired with C, while MUTYH removes adenine opposite 8-oxoG, comprising GO repair system. Accumulation links oxidative stress to aging, neurodegeneration, and cancer mutation signatures detected genome-wide. This principle illustrates essential molecular mechanisms governing replication fidelity and mutation fixation relevant for exam interpretation.