For each of the repair pathways listed below, please state whether, to accomplish gap filling, the pathway employs standard DNA replication enzymes (polymerase δ or ε; PCNA; DNA ligase I), or alternative DNA synthesis enzymes (β-family polymerases; XRCC1 or XRCC4; DNA ligase III or IV), or both (3 points)?
Short-patch base excision repair employs alternative enzymes, while long-patch repair employs standard enzymes, so the correct answer for (a) is "both". NER uses only the standard enzymes. Both non-homologous end joining and single-strand break repair employ alternative enzymes. Please see my lecture notes on the web for more information.
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