In contrast to this chromosome-counting mechanism, a single Y-linked gene called sex-determining region of the Y Sry determines sex in mice and most other mammals [ Swain and Lovell-Badge, ; Wilhelm et al. Inference of gene regulatory networks and compound mode of action from time course gene expression profiles.
Open in a separate window. Environmental Sex Determination. Estrogen and sex reversal in turtles: a dose-dependent phenomenon.
Rhen et al. Support Center Support Center. However, expression profiling alone does not test gene function and will not identify novel sex-determining genes or gene interactions.
An entirely different set of genes takes on this key role in mice i. Temperature-dependent sex determination in reptiles Location-dependent sex determination in Bonellia and Crepidula. Functional characterization of all these genes via reverse genetics in mice will be a very slow process.
Gonad Differentiation The basic pattern of gonad development is conserved in reptiles [ Raynaud and Pieau, ; Morrish and Sinclair, ]. Unlike the situation in mammals, sex determination in reptiles and birds is hormone-dependent.
The next step occurs when the bipotential primordium commits to develop as a testis or an ovary, a process commonly referred to environmental sex determination in reptiles snakes in Lancashire sex determination. Differentiation and development of testis in the oviparous lizard, Calotes versicolor Daud.
Other work centers on a theoretical model the Charnov — Bull model ,   predicted that selection should favour TSD over chromosome -based systems when "the developmental environment differentially influences male versus female fitness";  this theoretical model was empirically validated thirty years later  but the generality of this hypothesis in reptiles is questioned.
Ultrastructure des ebauches gonadiques du lezard vivipare Lacerta vivipara Jacquin pendant le periode de colonization par les gonocytes. Second, females can be produced at both temperature extremes and males at temperatures in the middle.
It is quite possible that there are other species of reptiles with more complicated scenarios of temperature reversal of chromosomal sex. The temperature-dependent sex determination drama: same cast, different stars.