While the master regulator gene Sry on the mammalian Y chromosome controls the switch for initiating male sex differentiation, many other species rely on environmental factors for gonadal sex differentiation. Yet other species, like zebrafish, appears to rely on a multitude of genetic cues for gonadal sex differentiation. Zebrafish gonadal differentiation initiates with the onset of a juvenile ...

Since the discovery of Sry in mammals [1, 2], few other master sex-determining genes have been identified in vertebrates [3-7]. To date, all of these genes have been characterized as well-known factors in the sex differentiation pathway, suggesting that the same subset of genes have been repeatedly and independently selected throughout evolution as master sex determinants [8, 9]. Here, we chara...

It is hypothesized on the basis of sex determination theory that species exhibiting genetic sex determination (GSD) may undergo sexual differentiation earlier in development than species with environmental sex determination (ESD). Most turtle species exhibit a form of ESD known as temperature-dependent sex determination (TSD), and in such species the chronology of sex differentiation is well st...