In this study, we genotyped seven SNPs covering the CHRNA5 and CHRNA3 genes in two independent samples selected from our previous twin studies. The first sample, denoted VAANX-ND (n = 815), was a combined sample of two previously used panels, the VAANX panel and the VAND panel [Chen et al., [2004], [2008]; Hettema et al., [2006]]. The second sample, denoted VAFTND (n = 1,121), included subjects who had FTQ/FTND assessments but were not used in the VAANX-ND sample. The characteristics of the markers typed were summarized in Table II. Two markers (rs6495308 and rs8192475) showed mild deviation from Hardy-Weinberg equilibrium. Their location and relative position to the genes were shown in Figure 1A. When linkage disequilibrium (LD) was examined, the two samples showed very similar pairwise LD (D′) among the typed SNPs (Fig. 1B,C). In both samples, rs16969968, rs578776, rs1051730, rs2869546, and rs6495308 were partitioned in a single LD block using default parameters. When haplotype structure was examined, both samples had the same major haplotypes and their frequencies were similar (data not shown). Our data were consistent with those from previous reports and the HapMap database.
