Fig. 1.

Variation in the numbers of intact V1R genes (filled bars) and pseudogenes (open bars) among mice, rats, humans, dogs, cows, and opossums with the phylogenetic relationships among the species shown by the tree. Mice have 187 functional V1Rs and 168 pseudogenes (11, 12). Rats have 102 functional V1Rs and at least 50 pseudogenes (ref. 12 and P.S., unpublished data). Humans have 4 V1R ORFs and ≈200 pseudogenes (9, 13). Cows have 32 functional V1Rs and 41 pseudogenes (this study). Dogs have 8 functional V1Rs and 22 pseudogenes (this study). Opossums have 49 functional V1Rs and 53 pseudogenes (this study). The number of pseudogenes in rats is likely an underestimate because there has been no comprehensive study of rat V1R pseudogenes.