Fig 1F shows a histogram of the iHS values for the CHRNB3-A6 cluster on chromosome 8. Summary statistics are shown in Table 1. Both the AFR and EUR populations show an excess of extreme iHS values (26.1% and 23.6%, respectively). By contrast, in the ASN population, there were few windows of extreme iHS scores and the overall proportion was not significantly different from the negative control. Several SNPs with extreme iHS values in these populations are contained within bins previously shown to be associated with either nicotine or cocaine dependence phenotypes [17,18]. Table 3 lists the SNPs from the LD bin showing genome-wide significance for reduced risk for nicotine dependence and provides the iHS value for rs1451240, the tag SNP. While there are several extreme values in AFR in the middle of this gene cluster, these values do not overlap with known SNPs related to nicotine dependence in this region. In EUR, 13 SNPs in this LD bin, including the tag SNP rs1451240, have extreme iHS values. All have positive values, indicating the presence of unusually long haplotypes containing the
