Sex Determination in Primates : the SRY Locus . Sex with your SOX on . Steven

Sex determination in all mammals is initiated by the Sry locus on the Y chromosome. Sry is a member of the large Sox HMG gene family postulated to have evolved from an ancestor of its paralogue on the Y chromosome, Sox3. This study investigates the relationship of Sry to the Sox genes of other animals, rooted against the HMG protein genes of a number of protists. It also looks at the evolution of Sry itself within the primates to ascertain whether Sry has differentially evolved amongst the widely varying lifestyles of the group. Two alignments are required for the analyses: just the HMG box of representative SOX proteins and the HMG outgroup, and a full length alignment of Sry from primates, rooted on Sry from the gray seal. Results corroborated but did not prove that Sry and Sox3 have a most recent common ancestor. Sox30 clustered with Sry in our tree as a paraphyletic group, and it had two Danio orthologues. Non-mammalian Sox-like sequences were absent only in the Sry, the Sox15, and the Sox7/Sox17/Sox18 clades. Sry appeared to have an intermediate rate of evolution compared to the Sox sequences we compared it to. The full length Sry phylogeny generally agreed with conventional primate trees. Two rapid bursts of evolution are associated with the diversification of the Old World apes and monkeys from the New World monkeys. Ka/Ks ratios were all over the place, presenting little