DNA samples from cocaine-dependent individuals of African-American decent (n=348; 72% male, mean age: 43) were collected during clinical studies of cocaine dependence at the University of Pennsylvania Treatment Research Center. Detailed sample characteristics are described elsewhere (Lohoff et al., 2008). DNA samples from control persons of African-American descent (n=257; 29% male, mean age: 40) were collected at the University of Pennsylvania, Thomas Jefferson University, and the National Institute of Mental Health Genetics Initiative (www.nimhgenetics.org). All protocols were approved by the Institutional Review Boards. The DRD3 gene is located on chromosome 3q13.3, contains 7 exons and spans 50,342bp (Ensembl accession ENST00000383673). SNPs for genotyping were selected using the tagging SNP algorithm based on available HapMap data with a minor allele frequency > 0.25 in the Yoruban population and a pairwise linkage disequilibrium (LD) r2 cutoff of > 0.8 (rs9825563; rs7625282; rs16822393; rs167770; rs2630349; rs3773678, rs9824856; rs9817063). The Ser9Gly SNP (rs6280) was added because of its implicated role in a variety of psychiatric disorders. SNP genotyping was performed using Applied Biosystems Inc. (ABI) 'Assays-on-demand' as per manufacturer protocol.
