Major histocompatibility complex class II DOA sequences from three Antarctic seal species verify stabilizing selection on the DO locus.

To provide additional support for the sequence conservation and hence the regulatory role of the MHC class II DOA locus, we obtained the nucleotide sequences of exon 2 and exon 3, along with the intervening intron, of the Ross seal, and sequences from the exon 2 region from the Weddell and leopard seals. These are the first reports of the sequences of this locus from a carnivore species. The results demonstrate strong conservation among mammals for the exon sequence and produce a gene genealogy that is consistent in topology with a species tree.