Hierarchical clusters for the HapMap data with a sample of 20K SNPs. (a) A total of 209 unrelated individuals from four populations are shown: CEU (60), YRI (60), CHB (45) and JPT (44). This figure shows a clustering result using 20K genome-wide random autosomal SNP loci. It is evident that YRI, CEU, CHB and JPT form four distinct clusters except for the misclassification of JPT28. Branch height represents dissimilarity. Notice that compared with YRI and CEU branch height, the CHB and JPT branch height is much shorter, representing that the genetic distance between these two populations is relatively close. This figure shows the partial cluster, for the full image please see additional file 2. (b) The magnified figure of CHB and JPT clusters in (a). This figure shows the partial cluster, for the full image please see additional file 3.