العربية
中国
Français
Deutsch
Ελληνική
हिन्दी
Italiano
日本語
Português
Русский
EspañolXY SEX-DETERMINATION SYSTEM
The 'XY sex-determination system' is the sex-determination system found in humans, most other mammals, some insects (''Drosophila'') and some plants (''Ginkgo''). In the XY sex-determination system, females have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males have two distinct sex chromosomes (XY), and are called the heterogametic sex.
The XY sex determination system was first described independently by Nettie Stevens and Edmund Beecher Wilson in 1905.
Some species (including most mammals) have a gene or genes on the Y chromosome that determine maleness. In the case of humans, a single gene (''SRY'') on the Y chromosome acts as a signal to set the developmental pathway towards maleness. Other mammals use several genes on the Y chromosome for that same purpose. Not all male-specific genes are located on the Y chromosome.
Other species (including most ''Drosophila'' species) use the presence of two X chromosomes to determine femaleness. One X chromosome gives putative maleness. The presence of Y chromosome genes are required for normal male development.
Humans, as well as some other organisms, can have a chromosomal arrangement that is contrary to their phenotypic sex, that is, XX males or XY females. See, for example, XX male syndrome and Androgen insensitivity syndrome.
★ X chromosome
★ Y chromosome, for more information about origins of the XY sex-determination system
★ chromosome, for information on abnormalities of the XY sex-determination system
★ intersexuality for information on variations in human sexual forms
★ X-inactivation
★ sexual differentiation, (human)
★ testis-determining factor
★ Barr body
★ Y-chromosomal Adam
★ Sex-determination system
★
★ X0 sex-determination system
★
★ ZW sex-determination system
★
★ Haplo-diploid sex-determination system
21016
★ Sex Determination and Differentiation
★ SRY: Sex determination from the National Center for Biotechnology Information
★ Sex Chromosomes: What Are They For?
The XY sex determination system was first described independently by Nettie Stevens and Edmund Beecher Wilson in 1905.
| Contents |
| Mechanisms |
| See also |
| References |
| External links |
Mechanisms
Some species (including most mammals) have a gene or genes on the Y chromosome that determine maleness. In the case of humans, a single gene (''SRY'') on the Y chromosome acts as a signal to set the developmental pathway towards maleness. Other mammals use several genes on the Y chromosome for that same purpose. Not all male-specific genes are located on the Y chromosome.
Other species (including most ''Drosophila'' species) use the presence of two X chromosomes to determine femaleness. One X chromosome gives putative maleness. The presence of Y chromosome genes are required for normal male development.
Humans, as well as some other organisms, can have a chromosomal arrangement that is contrary to their phenotypic sex, that is, XX males or XY females. See, for example, XX male syndrome and Androgen insensitivity syndrome.
See also
★ X chromosome
★ Y chromosome, for more information about origins of the XY sex-determination system
★ chromosome, for information on abnormalities of the XY sex-determination system
★ intersexuality for information on variations in human sexual forms
★ X-inactivation
★ sexual differentiation, (human)
★ testis-determining factor
★ Barr body
★ Y-chromosomal Adam
★ Sex-determination system
★
★ X0 sex-determination system
★
★ ZW sex-determination system
★
★ Haplo-diploid sex-determination system
References
21016
External links
★ Sex Determination and Differentiation
★ SRY: Sex determination from the National Center for Biotechnology Information
★ Sex Chromosomes: What Are They For?
This article provided by Wikipedia. To edit the contents of this article, click here for original source.
psst.. try this: add to faves
