Trends Genet 27 : — Reproduction, Fertility, and Development. Dufay M, Billard E How much better are females? Bibcode : PNAS. Environmental sex determination: sex is triggered by environmental cues, such as temperature, pH, social interactions, and seasonality e.
Please select a partnership to see additional information. Jana C. Systems that involve interacting somatic and germ line sex determination mechanisms may also limit transitions of sex-determining mechanisms, since changes in either germ line sex or somatic sex alone may produce infertile individuals .
Despite numerous theoretical predictions for how and why sex determination mechanisms change, many hypotheses remain untested.
J Embryol Exp Morphol 13 : 51— Shown are two-step pathways involving intermediate male- and female-sterile individuals. Sex determination in model species suggests that a master-switch gene e. In some flowering plants and fish, such as zebrafish, sex is determined by multiple genes polygenic sex determination.
In some flies and crustaceans, all offspring of a particular individual female are either exclusively male or exclusively female monogeny. At least one monotreme , the platypus , presents a particular sex determination scheme that in some ways resembles that of the ZW sex chromosomes of birds and lacks the SRY gene.
Trends Plant Sci 17 : — A full understanding of the diversity of sex determination mechanisms will require that we expand the taxonomic breadth of study systems well beyond classic model organisms. Furthermore, females switching from haplodiploidy would lose the fitness benefit associated with producing uniparental sons.
To date, only one example of the reversal of an ancient sex chromosome back to an autosome has been characterized.