Genomic DNA was extracted from whole blood obtained through venipuncture or from saliva samples (Oragene discs; DNA Genotek, Ottawa, Ontario, Canada). All SNPs were genotyped with 5′ exonuclease assays (Applied Biosystems Taq-Man predesigned or custom assays; Applied Biosystems, Foster City, California) (assay identification numbers and primer/probe sequences are available from the corresponding author) under standard conditions described previously.31 The overall genotyping completion rate exceeded 98% for each assay; the per-individual genotyping completion rate was at least 5 of 6 SNPs. None of the SNPs deviated from Hardy-Weinberg equilibrium as determined by contingency-table statistics (nominal P>.05; data not shown). Duplicate samples (at least 10% of all samples, randomly chosen, for each of the 6 SNPs) and no-template controls consistently yielded expected results.
