Total RNA was extracted from lymphoblastoid cell lines of the 726 individuals of 8 HapMap populations. The numbers of individuals of each population includes: CEU: 109 Caucasians living in Utah USA, of northern and western European ancestry, CHB: 80 Han Chinese from Beijing, China, GIH: 82 Gujarati Indians in Houston, TX, USA, JPT: 82 Japanese in Tokyo, Japan, LWK: 82 Luhya in Webuye, Kenya, MEX: 45 Mexican ancestry in Los Angeles, CA, USA, MKK: 138 Maasai in Kinyawa, Kenya, and YRI: 108 Yoruba in Ibadan, Nigeria (International HapMap Constortium 2005; Coriell, Camden, New Jersey, United States). Two in vitro transcription (IVT) reactions were performed as one-quarter scale Message Amp II reactions (Ambion, Austin, Texas, United States) for each RNA extraction using 200 ng of total RNA as previously described [13]. 1.5 µg of the cRNA was hybridized to an array [14]. For RNA extractions, IVT reactions, and array hybridizations, samples were processed in an order randomized with respect to population of origin.
