Trisomy 21: Difference between revisions

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Trisomy 21 is the name given to the most common occuring mutation that leads to [[Down's syndrome|Down syndrome]]. "[[Trisomy|Trisomy]]" because, due to a nondisjunction event (failed separation of the [[Chromosome|chromosome]]), there is an extra copy of [[Chromosome 21|chromosome 21]] in the gamete. And "21" states that the trisomy occurs on chromosome 21.   
Trisomy 21 is the name given to the non-disjunction of homologous pairs of chromosomes 21 which leads to [[Down's syndrome|Down syndrome]]. "[[Trisomy|Trisomy]]" because, due to a nondisjunction event (failed separation of the [[Chromosome|chromosome]] pairs to separate during stage 1 or 2 of meiosis), there is an extra copy of [[Chromosome 21|chromosome 21]] in one of the gametes. At fertilisation, this gamete will cause the zygote to contain 3 copies of the chromosome 21.     


The non-disjuntion event describes the failure of the chromosome pairs to separate properly during meiosis, either stage 1 or stage 2, thus leading to the trisomy of chromosome 21 where an extra copy of the chromosome is added.
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Revision as of 20:33, 2 December 2015

Trisomy 21 is the name given to the non-disjunction of homologous pairs of chromosomes 21 which leads to Down syndrome. "Trisomy" because, due to a nondisjunction event (failed separation of the chromosome pairs to separate during stage 1 or 2 of meiosis), there is an extra copy of chromosome 21 in one of the gametes. At fertilisation, this gamete will cause the zygote to contain 3 copies of the chromosome 21.     


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