Population genetics analysis of blood group-related genes

人ABO血型基因座有三种常见等位基因（A、B和O）。我们比较了这些等位基因的核苷酸序列，发现它们之间存在较大的核苷酸差异。这些差异对应于至少几百万年的分歧时间，这对于中性进化下的人类等位基因分歧来说是异常大的。我们构建了人类和非人类灵长类ABO等位基因的系统发育网络，观察到至少三个独立出现的B等位基因从祖先A型。这些结果表明，某种平衡选择可能已经在ABO基因座上运作。我们还构建了ABO及其进化相关的α-1，3-半乳糖基转移酶基因的系统发育树，这两个基因家族之间的分歧时间估计约为4亿年前。

There are three common alleles (A,B,and O) at the human ABO blood group locus. We compared nucleotide sequences of these alleles, and relatively large numbers of nucleotide differences were found among them. These differences correspond to the divergence time of at least a few million years, which is unusually large for a human allelic divergence under neutral evolution. We constructed phylogenetic networks of human and non-human primate ABO alleles, and at least three independent appearances of B alleles from the ancestral A form were observed. These results suggest that some kind of balancing selection may have been operating at the ABO locus. We also constructed phylogenetic trees of ABO and their evolutionarily related alpha-1,3-galactosyltransferase genes, and the divergence time between these two gene families was estimated to be roughly 400 million years ago.