Eight single nucleotide polymorphisms (SNPs) in CHRNA6 and CHRNB3 were chosen and genotyped as described in Zeiger et al. (2008). Briefly, SNPs were chosen to include those that have been previously examined by our group or others, and for which reliable genotyping assays were available. Figure 1 presents a diagram of the genes and the locations of the selected SNPs. It also shows linkage disequilibrium (r2) between SNPs in the Caucasian sub-sample and the predicted haplotype blocks based on current HapMap data (data release #21a). No LD data are given for rs35489610 due to the very low allele frequency. The SNPs previously genotyped were sufficient to capture the majority of known genetic variation. While some gaps exist, all of the SNPs in the regions of low LD are very rare with the exception of rs7017612 which shares high LD with SNPs in both LD blocks 1 and 2, but is flanked by rare SNPs. Following preamplification using the method of Zhang et al. (Zhang et al., 1992), TaqMan assays (ABI) were performed according to the manufacturer's instructions in a 384
