Which enzymatic activity allows DNA polymerases to excise mispaired bases immediately after incorporation during replication?
Answer and explanation
Correct answer: C. 3' to 5' exonuclease proofreading activity
Replicative DNA polymerases possess a distinct catalytic proofreading domain with 3' to 5' exonuclease activity. When a mismatched nucleotide is incorporated, the enzyme stalls, transfers the 3' terminus to the exonuclease site, excises the incorrect nucleotide, and resumes 5' to 3' synthesis. Endonucleases cut within DNA strands, topoisomerases relieve torsional strain, and telomerase extends chromosome ends.
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