We selected markers based on the Caucasian dataset of the HapMap project and positive association reports. For the interval covering the CHRNA5, CHRNA3, and CHRNB4 genes, we downloaded the Caucasian dataset from the HapMap website (http://www.hapmap.org) and used the HaploView program (version 4.0) to tag markers with frequency of 5% or greater. Markers with positive reports of association (rs16969968 and rs1051730) were included. Accordingly, we selected 7 SNPs covering the 55 kb genomic distance that encodes CHRNA5 and CHRNA3. No markers located in the CHRNB4 gene were selected, since markers in these three genes were in high LD as shown in HapMap database and previous reports, markers selected in CHRNA5 and CHRNA3 tagged those variants in CHRNB4 effectively.
