XRCC1 is a human gene that encodes a scaffold protein central to base excision and single‑strand break repair—the pathways that fix small chemical and oxidative lesions in DNA. The rs25487 change (often reported as Arg399Gln) is a well‑studied single nucleotide variant found frequently across populations and examined in genetic and environmental exposure research. At the protein level, XRCC1 brings together enzymes such as DNA ligase III, DNA polymerase beta, and interacting partners like PARP to coordinate repair of damaged bases and broken strands. Variation at rs25487 has been associated in studies with differences in repair efficiency and cellular responses to DNA‑damaging agents, making it relevant to understanding individual variation in handling genotoxic exposures.

Variants associated with reduced XRCC1 function may be linked to lower measured repair efficiency in laboratory and population studies and to greater cellular sensitivity to oxidative or chemical DNA damage. Conversely, genotypes associated with typical or stronger XRCC1 function tend to align with more efficient base excision and strand‑break repair in experimental settings. Interpretation of either pattern is most meaningful when combined with toxicant levels and other detox‑related genetic markers on the Toxin Zoomer, since repair capacity interacts with exposure burden and antioxidant pathways.

XRCC1 (rs25487) is included in the Toxin Zoomer to assess DNA repair capacity as part of the body’s response to environmental genotoxins. Evaluating this variant alongside measured toxicant loads helps clinicians contextualize whether exposures are likely to produce persistent DNA stress in someone with a given repair profile, aiding more personalized interpretation of exposure impact.