Practice question

Nitrous acid HNO2 is chemical mutagen acting by oxidative deamination converting primary amino groups to keto oxygen on nitrogenous bases. Adenine deaminates to hypoxanthine pairing as guanine, cytosine to uracil pairing as thymine, guanine to xanthine pairing as guanine analog yet pairing ambiguously. These conversions alter coding specificity because resulting deaminated bases form different hydrogen bond patterns during replication, leading predominantly to transition mutations without causing backbone breakage, distinguishing deaminative mechanism from alkylation or intercalation. This principle illustrates essential molecular mechanisms governing replication fidelity and mutation fixation relevant for exam interpretation.