Frequency distribution of FXI gene haplotypes observed in Ashkenazi Jews, Iraqi Jews, and Arabs. The numbers on the abcissa denote from bottom to top the allele numbers of polymorphisms in introns A, B, E, and M (as detailed in the legend of Fig 1). For instance, the haplotype designated 1211 is composed of allele 1 of intron A polymorphism, allele 2 of intron B polymorphism, allele 1 of intron E polymorphism, and allele 1 of intron M polymorphism. The lower and upper panels represent normal chromosomes and chromosomes bearing type II or type III mutations, respectively. Note that all chromosomes carrying the type II mutation are characterized by the same 1-2-2-2 haplotype that is observed in 8% to 12% of normal chromosomes. The chromosomes bearing the type III mutation are confined to Ashkenazi Jews, all characterized by haplotype 2-3-2-2.