Each pool was made in duplicate from the DNA of 25 subjects. Genomic DNA from each subject was diluted to approximately 10 μg/ml and the concentration determined using the Rediplate 96 PicoGreen assay (Invitrogen, Carlsbad CA). For each pool, 50 ng DNA of each subject was used, and the final pooled DNA was diluted to 300 μl with TE (0.1 mM EDTA, 10 mM Tris, pH 8.0). Each duplicate pool was made separately. There were six pools from Caucasian controls, eight pools from Caucasian former heroin addicts (cases), four pools from African American controls, and five pools from African American cases (Table 1).
