A Barr body is an inactivated X chromosome found in the somatic cells of most female mammals. It is a mechanism of dosage compensation to equalize the expression of X-linked genes between males (XY) and females (XX). The number of Barr bodies in a cell is typically one less than the total number of X chromosomes (N-1 rule). - Klinefelter syndrome (XXY): Individuals have 2 X chromosomes (N=2). Number of Barr bodies = 2 - 1 = 1. - Triple X syndrome (XXX): Individuals have 3 X chromosomes (N=3). Number of Barr bodies = 3 - 1 = 2. - Turner syndrome (XO): Individuals have only 1 X chromosome (N=1). Number of Barr bodies = 1 - 1 = 0. Thus, Barr bodies are absent. - Sub-human mammalian female individual (typically XX): Females have 2 X chromosomes (N=2). Number of Barr bodies = 2 - 1 = 1. Therefore, Barr bodies are absent in individuals with Turner syndrome.
Barr body is absent in somatic cell of
Asked in WBPSC CS Prelims 2017 · Topic: Genetic Disorders (Chromosomal Disorders: Numerical and Structural Aberrations)
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