DNA for genotyping was obtained from the cerebella of 266 of the total 269 samples in the collection and applied to either Illumina Infinium II 650K or Illumina Infinium HD Gemini 1M Duo BeadChips according to manufacturer’s protocols. Only genotypes common to both platforms are analysed here. Genotypes were called using BeadExpress software. SNPs were removed if the call rate was <98% (mean call rate for this study >99%), if not in Hardy–Weinberg equilibrium (P < 0.001) within Caucasian and within African American races separately, or not polymorphic (MAF <0.01). The total number of SNPs remaining in the analysis was 625,439 (96.2%).
