Trisomy 21: Difference between revisions

Latest revision as of 14:43, 9 December 2018

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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	~~ ~~Trisomy 21 is the name given to the ~~most common occuring mutation that~~ leads to [[Down's syndrome\|Down's syndrome]]. "Trisomy" because, due to a nondisjunction event (failed separation of the chromosome), there is an extra copy of ~~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\|non-disjunction]] of [[Homologous chromosomes\|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\|meiosis]]), there is an extra copy of [[Chromosome 21\|chromosome 21]] in one of the gametes. At [[Fertilisation\|fertilisation]], this [[Gamete\|gamete]] will cause the [[Zygote\|zygote]] to contain 3 copies of the chromosome 21.<br>

	~~The non-disjuntion event describes the failure of the chromosome pairs to separate properly during meiosis, either stage 1 or stage 2, such that~~ one of the gametes will contain 1 chromosome 21 ~~and one will contain 1 more, the latter being the trisomy~~.