XY sex-determination system

The XY sex-determination system is a <a href="/facts/Sex-determination_system/Ik7jhX8n">sex-determination system</a> present in many <a href="/facts/Mammal/phSwTzBo">mammals</a> (including <a href="/facts/Human/rlcTENsr">humans</a>), some insects (<a href="/facts/Drosophila/P4K7RkJl">Drosophila</a>), some snakes, some fish (<a href="/facts/Guppy/LgYJxylE">guppies</a>), and some plants (<a href="/facts/Ginkgo/4b2c7GeQ">Ginkgo</a> tree). 
In this system, the <a href="/facts/Sex/6VG77YCN">sex</a> of an individual usually is determined by a pair of <a href="/facts/Allosome/PGYGkTQM">sex chromosomes</a>. Typically, females have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males typically have two different kinds of sex chromosomes (XY), and are called the heterogametic sex. In humans, the presence of the Y chromosome is responsible for triggering male development; in the absence of the Y chromosome, the fetus will undergo female development. In most species with XY sex determination, an organism must have at least one <a href="/facts/X_chromosome/hpJxhSUr">X chromosome</a> in order to survive.
The XY system contrasts in several ways with the <a href="/facts/ZW_sex-determination_system/wzLkH7y5">ZW sex-determination system</a> found in <a href="/facts/Birds/RJF6zwLP">birds</a>, some insects, many <a href="/facts/Reptile/04n1uKf1">reptiles</a>, and various other animals, in which the heterogametic sex is female. A <a href="/facts/Temperature-dependent_sex_determination/HCMr7WdB">temperature-dependent sex determination</a> system is found in some reptiles and fish.

XY sex-determination system open-in-new

XY sex-determination system