In this study, we analyzed duplicate pooled DNA samples using the GeneChip Mapping 100K Set. Pools were formed by combining an equal amount of DNA from 25 subjects (Table 1). A total of 200 Caucasian former heroin addicts (cases), 150 Caucasian controls, 125 African American cases, and 100 African American controls were used to make the pools. More than 113,000 variants were examined in each ethnicity (see Data analysis).
