The XY system contrasts in several ways with the ZW sex-determination system found in birdssome insects, many reptilesand various other animals, in which the heterogametic sex is female. Nat Rev Genet 10 : — Small mutations would accumulate slowly and the two populations would be selected for different traits.
Aristotle claimed in error that the male principle was the driver behind sex determination,  such that if the male principle was insufficiently expressed during reproduction, the fetus would develop as a female. Figure 2. Dev Genes Evol : — Utrecht University - Department of Biology.
Schematic xy system of sex determination in Wodonga of some sex determination SD mechanisms. We [are] entering this new era in molecular biology of sex determination where it's a more subtle dosage of genes, some pro-males, some pro-females, some xy system of sex determination in Wodonga, some anti-females that all interplay with each other rather than a simple linear pathway of genes going one after the other, which makes it very fascinating but very complicated to study.
Males typically have two different kinds of sex chromosomes XYand are xy system of sex determination in Wodonga the heterogametic sex. Additionally, an abnormal number of sex chromosomes aneuploidy may be present, such as Turner's syndromein which a single X chromosome is present, and Klinefelter's syndromein which two X chromosomes and a Y chromosome are present, XYY syndrome and XXYY syndrome.
There are some reptiles, such as the boa constrictor and Komodo dragon that can xy system of sex determination in Wodonga both sexually and asexually, depending on whether a mate is available. Mol Ecol 9 : —
In these species, one or more genes are present on their Y chromosome that determine maleness. Heterochromatin molecular and structural aspects. Curr Opin Genet Dev 20 : — Many other sex-determination systems exist.
In species with genotypic sex determination, the chromosome pair that determines sex can change rapidly over time. A reliable, non invasive PCR method for giant panda Ailuropoda melanoleuca sex identification.