Total RNA was extracted from lymphoblastoid cell lines of the 270 individuals of the HapMap (22; Coriell, Camden, New Jersey, United States). Two, one-quarter scale Message Amp II reactions (Ambion, Austin, Texas, United States) were performed for each RNA extraction using 200 ng of total RNA as previously described 18. 1.5 μg of the cRNA was hybridized to an array 19.
