DNA was extracted from blood samples, and cell lines were developed as an additional DNA source. Samples were genotyped using lllumina Human1Mv1_CBeadChip at the Johns Hopkins Center for Inherited Disease Research (CIDR). Extensive and rigorous data cleaning was employed (Laurie et al., 2010), resulting in quality-controlled genotypic data for 948,658 SNPs (Bierut et al., 2010).
