Fig 6. The phylogenetic analysis using the amino acid sequences of the B2M gene among ten mammalian species including whale (intact, XM004281255; retrogene, NW004438467), pig (L13854), cattle (BC118352), goat (XM013967395), sheep (NM001009284), horse (NM001082502), cat (NM001009876), dog (NM001284479), human (NM004048) and mouse (NM009735).

Unrooted phylogenetic trees were constructed from 116–125 amino acids in length, from translated B2M of ten species using the maximum likelihood method and the representative tree was shown. The numbers on the nodes indicate the bootstrap values above 50% (n = 1000). Whale_retro indicates the retrotransposon copy of the B2M gene in whale. The node of pig represents for both copies of B2M with the identical amino acid sequence.