XRCC1 and colorectal cancer: Similarly, although polymorphisms in exons 6 and 10 of the XRCC1 gene, that is involved in BER and the repair of single-strand DNA breaks, have been associated with colorectal cancer (reviewed in de Jong et al, 2002) and a range of other internal cancers (Sturgis et al, 1999; Chen et al, 2002; Duell et al, 2002; Stern et al, 2002), no association was seen in our study between the XRCC1 exon 17 polymorphism and colorectal cancer.