D' LD plot for the XRCC5 gene was calculated using CEU genotype data for the markers genotyped across this region. Prefixes to SNP IDs denote the studies that SNPs were genotyped in: HT_ for the Hayden/Tewari study and J_ for the Johnston et al study. LD (linkage disequilibrium) blocks were defined using the 4 gamete rule. D' = 1 between the SNPs rs1051677, rs1051685, and rs6941.