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Barr's body

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Mass of condensed sex chromatin in the nuclei of normal female somatic cells due to inactive X chromosome. Barr and Ewart George Bertram (1923–)showed that it is possible to determine the genetic sex of an individual according as to whether there is a chromatin mass present on the inner surface of the nuclear membrane of cells with resting or intermitent nuclei (sex chromatin).

According to the Lyon hypothesis, one of the two X xhromosomes in each somatic cell of the female is genetically inactivated. The Barr body represents the inactivated X chromosome. X inactivation occurs around the 16th day of embryonic development. The term Barr body was introduced by Mary Lyon.


  • M. L. Barr and E. G. Bertram:
    A morphological distinction between neurones of the male and female, and the behaviour of the nucleolar satellite during accelerated nucleoprotein synthesis.
    Nature, London,1949, 163: 676-677.
  • Keith Leon Moore (1925–), M. A. Graham and M. L. Barr:
    The detection of chromosomal sex in hermaphrodites from a skin biopsy.
    Surgery, Gynecology and Obstetrics, Chicago, 1953, 96: 641-648.
    Sex chromatin demonstrated in humans.
  • M. L. Barr:
    Testicular dysgenesis affecting the seminoferous tubules principally with chromatinpositive nuclei.
    The Lancet, London, 1956, 1: 853-856.
  • M. L. Barr:
    Sex chromatine and phenotype in man. Disagreement between nuclear sex and phenotype raises questions about the cause of sex anomalies.
    Science, Washington, 1959, 30: 679-735.
  • B. H. Barr:
    An unusual sex chromatin pattern in three mentally deficient subjects.
    Journal of Mental Deficiency Research, Oxford, 1963, 3: 78-87.

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