For this replication study, the SNP rs4956302 was selected due to the fact that it achieved the highest significance for association with smoking status among all the SNPs tested genome-wide. The SNP rs17354547 was selected because it is highly conserved across multiple species. The other two SNPs (rs4956396 and rs1402812) were randomly selected from the remaining seven SNPs since these seven SNPs are in high LD and achieved similar p values (Figure 1).
