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A Barr body (named after discoverer Murray Barr) [1] or X-chromatin is an inactive X chromosome. In species with XY sex-determination (including humans), females typically have two X chromosomes, [ 2 ] and one is rendered inactive in a process called lyonization .
The inactive X forms a discrete body within the nucleus called a Barr body. [38] The Barr body is generally located on the periphery of the nucleus, is late replicating within the cell cycle, and, as it contains the Xi, contains heterochromatin modifications and the Xist RNA.
Xist will be continuously created to maintain a condensed and silenced Barr body. [ 9 ] [ 10 ] [ 11 ] In human cells with more than one X chromosome, two long non-coding RNAs are produced: Tsix is produced by one X chromosome, and Xist is produced by all of the other X chromosomes.
The Barr body is indicated by the arrow. They are only present in cells with XX chromosomes. This was the evidence searched for in Barr body tests of samples from female athlete's inner cheeks. From 1958 to 1992, all female athletes underwent mandatory sex verification tests before taking part in any IAAF or IOC event.
Nuclear sexing can be done by identifying Barr body, a drumstick like appendage located in the rim of the nucleus in somatic cells. Barr body is the inactive X chromosome which lies condensed in the nucleus of somatic cells. A typical human (or other XY-based organism) female has only one Barr body per somatic cell, while a typical human male ...
Thus, Ohno described the "n-1" rule to predict the number of Barr bodies in a female with n number of X chromosomes in her karyotype. [ 6 ] Simultaneously, Mary F. Lyon began investigating manipulations of X-linked traits that had phenotypically visible consequences, particularly in mice, whose fur color is a trait intimately linked to the X ...
Turner syndrome (TS), commonly known as 45,X, or 45,X0, [note 1] is a chromosomal disorder in which female cells have only one X chromosome instead of two, or are partially missing an X chromosome (sex chromosome monosomy) leading to the complete or partial deletion of the pseudoautosomal regions (PAR1, PAR2) in the affected X chromosome.
Murray Llewellyn Barr OC FRSC FRS [1] (June 20, 1908 – May 4, 1995) was a Canadian physician and medical researcher who discovered with graduate student Ewart George Bertram, in 1948, an important cell structure, the "Barr body".