Barr body
Barr body
Barr body (pronounced: /bɑːr ˈbɒdi/), also known as sex chromatin, is a structure found in the nucleus of female mammalian cells. It was first discovered by Canadian scientist Murray Barr in 1949.
Etymology
The term "Barr body" is named after its discoverer, Murray Barr. The term "sex chromatin" is derived from its role in sex determination in mammals.
Definition
A Barr body is an inactivated X chromosome in a cell of a female mammal. It is visible as a dense, dark-staining spot at the periphery of the nucleus. The presence of a Barr body typically indicates that the organism has two X chromosomes, and is therefore genetically female.
Function
The primary function of the Barr body is to compensate for the genetic imbalance between males and females. Males have one X chromosome and one Y chromosome (XY), while females have two X chromosomes (XX). To ensure that females, like males, have one functional copy of the X chromosome in each body cell, one of the X chromosomes in each cell of a female is inactivated and becomes a Barr body.
Related Terms
- X-inactivation: The process by which one of the two copies of the X chromosome present in female mammals is inactivated.
- Lyon hypothesis: The hypothesis proposed by British geneticist Mary F. Lyon that explains the process of X-inactivation.
- Sex determination: The biological system that determines the development of sexual characteristics in an organism.
External links
- Medical encyclopedia article on Barr body
- Wikipedia's article - Barr body
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