XY sex-determination system
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The XY sex-determination system is a well-known sex-determination system. It is found in human beings and other mammals. In the XY sex-determination system, females have two of the same kind of sex chromosome (XX), while males have two distinct sex chromosomes (XY). Some species (including humans) have a gene SRY on the Y chromosome that determines maleness; others (such as the fruit fly) use the presence of two X chromosomes to determine femaleness.
SRY is not the only male-determining gene in mammals, or even the most common: most non-primate mammals use a different Y-chromosome gene, UBE1, for this purpose. Also, two species of "mole voles", Ellobius tancrei and E. lutescens, have lost the Y chromosome entirely. In one species, both sexes have unpaired X chromosomes; in the other, both females and males have XX.
See also
- chromosome, for information on abnormalities of the XY sex-determination system
- intersexual for information on variations in human sexual forms
- sexual differentiation, (human)
- testis-determining factor
- Barr body
- Y-chromosomal Adam
