The HapMap CEU haplotype data revealed four major haplogroups (Figure 2b): 1) the “reference” group (“REF”, ~36%) with no variants (including the reference 118A allele and the reference intron 1 sequence); 2) the block 2 group (~22%); 3) the 118G group (~15%) with additional variants in block 1; and 4) the intron 1 variants of block 4 (“INT1”, ~11%). The minor haplogroups are: block 3 (4%) and 12% of the haplotypes that could not be assigned to one of the major haplogroups (grouped as “Others” in Figure 2b). Of the 59 HapMap CEU subjects, ten (17%) were homozygous for the “REF” haplogroup, two (3%) were homozygous for the 118G haplogroup, and five (8%) were homozygous for the block 2 haplogroup. No individual was homozygous for the “INT1” haplogroup and one was heterozygous for the “118G”/“INT1” groups. All the rest were heterozygotes with different allelic combinations.
