Figure 1: CD6 and CD5 genes map to contiguous regions in mammalian and birds and are supposed to have arisen for implication of a common ancestral gene. CD6 is orthologue to the amphibian protein CD5/CD6 and the fish protein 14d8. Data has been taken from the genome database (http://www.ensembl.org/) and from previously published results [11, 13]. Black boxes represent the exons encoding the extracellular SRCR domains. First and last exons are depicted when known. Legend: HERV human endogenous retrovirus; CA: microsatellite repeat, My: million year.