Klinefelter's syndrome causes: Difference between revisions
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==Overview== | ==Overview== | ||
==Causes== | |||
[[Image:XXY syndrome.svg.png|250px|thumb|left|XXY syndrome]] | [[Image:XXY syndrome.svg.png|250px|thumb|left|XXY syndrome]] |
Revision as of 20:40, 14 August 2012
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Causes

The extra X chromosome is retained because of a nondisjunction event during meiosis I (gametogenesis). Nondisjunction occurs when homologous chromosomes, in this case the X and Y sex chromosomes, fail to separate, producing a sperm with an X and a Y chromosome. Fertilizing a normal (X) egg produces an XXY offspring.
The XXY chromosome arrangement is one of the most common genetic variations from the XY karyotype, occurring in about 1 in 500 live male births.
Another mechanism for retaining the extra X chromosome is through a nondisjunction event during meiosis II in the female. Nondisjunction will occur when sister chromatids on the sex chromosome, in this case an X and an X, fail to separate. An XX egg is produced which, when fertilized with a Y sperm, yields XXY offspring.