Concerted evolution events among BEX , WEX and GASP genes. Maximum likelihood phylogenetic trees for A) the first exon of the 5'UTR of BEX2, BEX3 and GASP4 genes B) the first exon of the 5' UTR of WEX2, WEX8 and WEX1 genes, and C) the exonic 5' UTR of GASP1 and GASP2 genes. 5' UTR sequences were extracted either from sequence transcripts or from homologous genomic regions. Maximum likelihood tree topologies and branch lengths were obtained using the program BASEML , for a given DNA sequence alignment. Each alignment was bootstrapped a 1000 times using the neighbour-joining method, and bootstrap values were overlaid the maximum likelihood tree. Abbreviations: Hs, Homo sapiens; Mm, Mus musculus; Rn, Rattus norvegicus; Cf, Canis familiaris.