The 11 common haplotypes are derived from recombination of a small number of haplotypes. The figure shows the putative mechanism for formation of common recombinant haplotypes from parental haplotypes by reciprocal recombination. All 11 haplotypes can be accounted for by recombination at the recombination hotspot near 2DL4. The mechanism effectively swaps the centromeric and telomeric motifs (identification in key above) between haplotypes by reciprocal recombination. Genes are not duplicated or deleted by this process, but haplotype motifs are interchanged. Some recombinations generate equivalent recombinant haplotypes to the others, in terms of gene content and not considering alleles. (Right) Constituent haplotype motifs based on gene content; (f) frequency. The numbers in the parentheses refer to haplotypes defined in Figure 1. Where there are two haplotypes in parentheses, e.g., (01/02), then these haplotypes only differ by 2DS4 type (2DS4f or 2DS4v; see below). (Gray) Cen-B and Tel-B motif genes; (white) Cen-A and Tel-A motif genes. cA01 and tA01 denote Cen-A haplotype motif 1 and Tel-A haplotype motif 1, respectively. tA01 may have either form of 2DS4 (2DS4f or 2DS4v). tB01 may have either variant of 2DS3S5 (2DS3 or 2DS5). The arrows point both up and down because the precursor and recombinant haplotypes are not known and the process could occur in either direction, exchanging parental and progeny haplotypes.
