406209.fig.008
Figure 8: A scheme of the evolutionary pathway of some haplogroups of the human ABO blood group genes. Red square indicates the A type gene. Black vertical bar indicates Δ261 in exon 6. The blue portion of the B gene indicates the two B type-specific critical amino acid sites; containing region in exon 7. Stars indicate recombination event. A rough time scale is shown by following the results of [6]; the divergence time of the lineage leading to B101: 2.08 million years ago, the divergence time of the lineage leading to O01: 1.98 million years ago, and the divergence time of the lineage leading to A101: 0.26 million years ago. Because times of divergence between A and O02, the Δ261 deletion, transfer of Δ261, two amino acid substitutions for B101, and recombination for O02/B101 cannot be estimated, these positions are located arbitrarily.