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Information about Xy 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.

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

References

21016

External links

A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that
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Mammalia
Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

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Drosophila
Fallén, 1823

Type species
Drosophila funebris[1]
(Fabricius, 1787)

Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more
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Ginkgoaceae

Genus: Ginkgo

Species
G. biloba L.
The Ginkgo (Ginkgo biloba; '銀杏' in Chinese), frequently misspelled as "Gingko", and also known as the
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Sex refers to the male and female duality of biology and reproduction. Unlike organisms that only have the ability to reproduce asexually, sexed male and female pairs have the ability to produce offspring through meiosis and fertilization.
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Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division.]] A chromosome is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell.
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Homogametic sex refers to the gender of a species in which both sex chromosomes are identical. For example, in humans, females, with two X sex chromosomes, would be referred to as the homogametic sex while males, with one X and one Y sex chromosomes, would be referred to as the
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Nettie Maria Stevens (July 7,1861 - May 4,1912) was an early American geneticist. She and Edmund Beecher Wilson were the first researchers to describe the chromosomal basis of sex.
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Edmund Beecher Wilson
Born September 19 1856(1856--)
Geneva, Illinois
Died March 3 1939 (aged 84)

Nationality USA
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19th century - 20th century - 21st century
1870s  1880s  1890s  - 1900s -  1910s  1920s  1930s
1902 1903 1904 - 1905 - 1906 1907 1908

Year 1905 (MCMV
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For a non-technical introduction to the topic, see .
A gene is a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions and/or other functional sequence regions.
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The Y chromosome is the sex-determining chromosome in humans and most other mammals. In mammals, it contains the gene SRY, which triggers testis development, thus determining sex.

Overview

Most mammals have one pair of sex chromosomes in each cell.
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SRY (Sex-determining Region Y) is a sex-determining gene on the Y chromosome in humans and other primates. It is not the only, or even most common sex-determining gene in mammals. Most non-primate mammals use the Y chromosome gene UBE1 for the same purpose.
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Drosophila
Fallén, 1823

Type species
Drosophila funebris[1]
(Fabricius, 1787)

Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more
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The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals (the other is the Y chromosome). It is a part of the XY sex-determination system and X0 sex-determination system.
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XX male syndrome (also called de la Chapelle syndrome) is a rare sex chromosomal disorder in men. Usually it is caused by unequal crossing over between X and Y chromosomes during meiosis. Symptoms include small testes, gynecomastia and sterility.
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Androgen insensitivity syndrome
Classification & external resources

Testosterone (structure pictured) and dihydrotestosterone to a lesser degree, are the primary androgens involved in AIS.
ICD-10 E 34.5
ICD-9 259.
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The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals (the other is the Y chromosome). It is a part of the XY sex-determination system and X0 sex-determination system.
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The Y chromosome is the sex-determining chromosome in humans and most other mammals. In mammals, it contains the gene SRY, which triggers testis development, thus determining sex.

Overview

Most mammals have one pair of sex chromosomes in each cell.
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Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division.]] A chromosome is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell.
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Intersexuality is the state of a person whose sex chromosomes, genitalia and/or secondary sex characteristics are determined to be neither exclusively male nor female. A person with intersex may have biological characteristics of both the male and female sexes.
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X-inactivation (also called lyonization) is a process by which one of the two copies of the X chromosome present in female mammals is inactivated. The inactive X chromosome is silenced by packaging in repressive heterochromatin.
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Sexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote (fertilized egg). As male and female individuals develop from zygotes into fetuses, into infants, children, adolescents, and eventually into adults, sex
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Testis-determining factor (TDF) is a general term for the gene (or product thereof) that results in maleness in humans and some other species.

Certain genes cause chemical reactions that result in the development of testes.
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Barr body is the inactive X chromosome in a female cell, or the inactive Z in a male (Lyon, 2003), rendered inactive in a process called Lyonization. The Lyon hypothesis states that in cells with multiple X chromosomes, all but one is inactivated during mammalian embryogenesis
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In human genetics, Y-chromosomal Adam (Y-mrca) is the patrilineal human most recent common ancestor (mrca) from whom all Y chromosomes in living men are descended. Y-chromosomal Adam is thus the male counterpart of Mitochondrial Eve (the mt-mrca), the matrilineal human most
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A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that
..... Click the link for more information.
The X0 sex-determination system is a system that grasshoppers, crickets, roaches, and some other insects use to determine the sex of their offspring. In this system, there is only one sex chromosome, referred to as X.
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The ZW sex-determination system is a system that birds, some fishes, and some insects (including butterflies and moths) use to determine the sex of their offspring. The ovum determines the sex of the offspring in this system, in contrast to the XY sex-determination system and the
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