All raw intensity files were loaded in Illumina's GenomeStudio v3, normalized and clustered using the SNP manifest and cluster files for build37 of the human genome. In all our analyses we used the total signal intensity R for each SNP, which is the sum of the normalized X (“A” allele, Cy5 red) and Y (“B” allele, Cy3 green) intensities. We also used the B allele frequency (BAF), which is a modified version of the allelic intensity ratio theta (θ = 2/p*arctan(Y/X)), to reduce SNP-to-SNP variation in theta using the canonical clusters.