TaqMan® SNP genotyping assays were developed for each of the SNPs used in the current study (Supplementary Table S1) and are commercially available (Applied Biosystems, Foster City, CA; cf. www.allsnps.com). Assays were performed with the TaqMan Genotyping Master Mix, using conditions recommended by the manufacturer, on an ABI 7900 Sequence Detection System (Applied Biosystems, Foster City, CA).