Vertebrate sex determination: many means to an end. Embryos were allocated to 1 of 4 groups at stage 15, including non-treated and vehicle-treated controls, a dihydrotestosterone- DHT treated group, a flutamide- Flut treated group, and a group treated with both DHT and Flut. J Endocrinol.
Biol Reprod. Yet, the mechanisms underlying the development of morphological, physiological, and behavioral differences between the sexes have been elucidated in detail in just a few species. The temperature-dependent sex determination drama: same cast, different stars.
Sex determination in loggerhead turtles: differential expression of two hnRNP proteins.
Their sexual fate is determined by the temperature of the environment during the thermosensitive period TSP of incubation, which regulates aromatase activity. All sex chromosomes started out as an original autosome of an original amniote that relied upon temperature to determine the sex of offspring.
By a gradual process of genetic instability, which may have been related to failure in the recombination process, the chromosomes have begun to differ from each other. Four evolutionary strata on the human X chromosome. One way to discern between the two theories would be to look into different combinations of Z and W chromosomes.
Once spermatogenesis is over and the hermaphrodite enters its mature stage Mthe original sex determination pathway is re-established tra-2 becomes active again in the germline of adult hermaphrodites and makes the switch to oogenesis by inactivating the genes fem, fog-1 and fog-3 gene products that allowed spermatogenesis.
Lance  identified a shortcoming of such studies: a candidate gene approach that depends on homologs of mammalian sex-determining genes will not identify new or unique sex-determining genes in reptiles. Most research on the molecular biology of sex determination in reptiles describes expression patterns for orthologs of mammalian sex-determining genes.
Charles Darwin first provided a lucid explanation of how gender differences evolve nearly years ago. Oestrogens and temperature-dependent sex determination in reptiles: all is in the gonads. Embryological ontogeny of aromatase gene expression in Chrysemys picta and Apalone mutica turtles: Comparative patterns within and across temperature-dependent and genotypic sex-determining mechanisms.
Bergeron et al. Taken together, these observations indicate that genes transduce temperature into a biological signal for sex determination. In brief, equal or approximately equal numbers of viable eggs from each clutch were assigned to one of 4 hormone treatments to control for clutch differences.
BMC Dev Biol. Int Comp Biol. Conclusions Fundamental similarities in gonad development are evident at the genetic, molecular, cellular, developmental, and physiological levels in all vertebrates.