We quantified gene expression in the 270 individuals genotyped in the International HapMap Project with Illumina's human whole-genome expression (WG-6 version 1) arrays which contain 47,294 probes in 4 technical replicates as described in 19. The population samples include 30 Caucasian trios of Northern and Western European origin (CEU), 45 unrelated Chinese individuals from Beijing University (CHB), 45 unrelated Japanese individuals from Tokyo (JPT), and 30 Yoruba trios from Ibadan, Nigeria (YRI). Expression signal values were log2 transformed and normalized using quantile normalization across the four replicates of an individual followed by median normalization across all 270 individuals to allow comparison of expression values across populations 24,25.
