Genomic DNA was isolated from buccal cell swabs and preamplified using the method of Zhang et al (Zhang et al, 1992). Data obtained using this DNA are high-quality; these methods have been shown to be reliable for genotyping (Anchordoquy et al, 2003; Haberstick and Smolen, 2004). A Biomek® 3000 Laboratory Automation Workstation (Beckman Coulter) was used to automate DNA genotyping assay preparation in a 384 well plate format. TaqMan® assays for allelic discrimination (Applied Biosystems) were used to determine SNP genotypes, per instructions of the manufacturer under standard conditions using an ABI PRISM® 7900 instrument. In total, eight SNPs located in the CHRNA6 – CHRNB3 region of chromosome 8 were genotyped in 1051 subjects.
