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Nondisjunction sex chromosomes

Sharp, Miranda Durkie, Terry J. Hassold, Andrew R. Collins, Patricia A. Human trisomy is attributable to many different mechanisms and the relative importance of each mechanism is highly chromosome specific. The association between altered recombination and maternal non-disjunction is well documented: reductions in recombination have been reported for maternal meiosis I MI errors involving chromosomes 15, 16, 18 and 21 and increased recombination has been reported for meiosis II MII errors involving chromosome We therefore investigated maternal X chromosome non-disjunction, to determine whether the effects of recombination are unique to the X chromosome or similar to any of the autosomes thus far studied.
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Nondisjunction and chromosomal anomalies

Uroz, C. In humans, little is known about the mechanisms of non-disjunction working in male meiosis, although considerable attention has been given to these mechanisms in female meiosis. The present study explores the origin of meiotic non-disjunction during human spermatogenesis and the chromosomes most commonly involved in this process. Testicular biopsy was obtained during a vasectomy procedure.
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Maternal sex chromosome non-disjunction: evidence for X chromosome-specific risk factors

Mostapha Ahmad 1 , Silvera-Redondo C. Nondisjunction is the failure of homologous chromosomes to disjoin correctly during meiosis. This results in the production of gametes containing a greater or lesser chromosomal amount than normal ones.
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Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division. There are three forms of nondisjunction: failure of a pair of homologous chromosomes to separate in meiosis I , failure of sister chromatids to separate during meiosis II , and failure of sister chromatids to separate during mitosis. Calvin Bridges and Thomas Hunt Morgan are credited with discovering nondisjunction in Drosophila melanogaster sex chromosomes in the spring of , while working in the Zoological Laboratory of Columbia University. In general, nondisjunction can occur in any form of cell division that involves ordered distribution of chromosomal material. Higher animals have three distinct forms of such cell divisions: Meiosis I and meiosis II are specialized forms of cell division occurring during generation of gametes eggs and sperm for sexual reproduction, mitosis is the form of cell division used by all other cells of the body.
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