Down syndrome causes: Difference between revisions
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==Overview== | ==Overview== | ||
Down's syndrome (DS) is caused due to the presence of an extra 21st [[chromosome]] (triplication of [[Chromosome 21 (human)|chromosome 21]]). 95 percent of DS cases are due to [[Meiotic nondisjunction|meiotic non-disjunction]] during [[meiosis I]]. 4 percent of DS cases arise due to [[Robertsonian translocation]] and very rarely DS may be caused a post-[[fertilization]] [[Mitosis|mitotic]] error ([[mosaicism]]). | |||
==Causes== | ==Causes== | ||
Down's syndrome is caused by triplication of chromosome 21 (trisomy 21). The aneuploidy may occur in three possible ways: | Down's syndrome is caused by triplication of [[Chromosome 21 (human)|chromosome 21]] (trisomy 21). The [[aneuploidy]] may occur in three possible ways: | ||
* '''Meiotic nondisjunction of homologous chromosomes''' | * '''Meiotic nondisjunction of homologous chromosomes''' | ||
** From improper division of chromosomes during meiosis I or meiosis II. One gamete will end up with extra 21st chromosome.<ref name="pmid1825697">{{cite journal |vauthors=Antonarakis SE |title=Parental origin of the extra chromosome in trisomy 21 as indicated by analysis of DNA polymorphisms. Down Syndrome Collaborative Group |journal=N. Engl. J. Med. |volume=324 |issue=13 |pages=872–6 |date=March 1991 |pmid=1825697 |doi=10.1056/NEJM199103283241302 |url=}}</ref><ref name="pmid1347192">{{cite journal |vauthors=Antonarakis SE, Petersen MB, McInnis MG, Adelsberger PA, Schinzel AA, Binkert F, Pangalos C, Raoul O, Slaugenhaupt SA, Hafez M |title=The meiotic stage of nondisjunction in trisomy 21: determination by using DNA polymorphisms |journal=Am. J. Hum. Genet. |volume=50 |issue=3 |pages=544–50 |date=March 1992 |pmid=1347192 |pmc=1684265 |doi= |url=}}</ref> | ** From improper division of [[chromosomes]] during [[meiosis I]] or [[Meiosis|meiosis II]]. One [[gamete]] will end up with extra 21st [[chromosome]].<ref name="pmid1825697">{{cite journal |vauthors=Antonarakis SE |title=Parental origin of the extra chromosome in trisomy 21 as indicated by analysis of DNA polymorphisms. Down Syndrome Collaborative Group |journal=N. Engl. J. Med. |volume=324 |issue=13 |pages=872–6 |date=March 1991 |pmid=1825697 |doi=10.1056/NEJM199103283241302 |url=}}</ref><ref name="pmid1347192">{{cite journal |vauthors=Antonarakis SE, Petersen MB, McInnis MG, Adelsberger PA, Schinzel AA, Binkert F, Pangalos C, Raoul O, Slaugenhaupt SA, Hafez M |title=The meiotic stage of nondisjunction in trisomy 21: determination by using DNA polymorphisms |journal=Am. J. Hum. Genet. |volume=50 |issue=3 |pages=544–50 |date=March 1992 |pmid=1347192 |pmc=1684265 |doi= |url=}}</ref> | ||
* '''Robertsonian translocation''' | * '''Robertsonian translocation''' | ||
** Individuals with normal number of chromosomes but an extra portion of 21st chromosome.<ref name="pmid6238567">{{cite journal |vauthors=Hook EB |title=Parental age and unbalanced Robertsonian translocations associated with Down syndrome and Patau syndrome: comparison with maternal and paternal age effects for 47, +21 and 47, +13 |journal=Ann. Hum. Genet. |volume=48 |issue=Pt 4 |pages=313–25 |date=October 1984 |pmid=6238567 |doi= |url=}}</ref><ref name="pmid25932913">{{cite journal |vauthors=Zhao WW, Wu M, Chen F, Jiang S, Su H, Liang J, Deng C, Hu C, Yu S |title=Robertsonian translocations: an overview of 872 Robertsonian translocations identified in a diagnostic laboratory in China |journal=PLoS ONE |volume=10 |issue=5 |pages=e0122647 |date=2015 |pmid=25932913 |pmc=4416705 |doi=10.1371/journal.pone.0122647 |url=}}</ref><ref name="pmid1831959">{{cite journal |vauthors=Petersen MB, Adelsberger PA, Schinzel AA, Binkert F, Hinkel GK, Antonarakis SE |title=Down syndrome due to de novo Robertsonian translocation t(14q;21q): DNA polymorphism analysis suggests that the origin of the extra 21q is maternal |journal=Am. J. Hum. Genet. |volume=49 |issue=3 |pages=529–36 |date=September 1991 |pmid=1831959 |pmc=1683126 |doi= |url=}}</ref> | ** Individuals with normal number of [[chromosomes]] but an extra portion of 21st [[chromosome]].<ref name="pmid6238567">{{cite journal |vauthors=Hook EB |title=Parental age and unbalanced Robertsonian translocations associated with Down syndrome and Patau syndrome: comparison with maternal and paternal age effects for 47, +21 and 47, +13 |journal=Ann. Hum. Genet. |volume=48 |issue=Pt 4 |pages=313–25 |date=October 1984 |pmid=6238567 |doi= |url=}}</ref><ref name="pmid25932913">{{cite journal |vauthors=Zhao WW, Wu M, Chen F, Jiang S, Su H, Liang J, Deng C, Hu C, Yu S |title=Robertsonian translocations: an overview of 872 Robertsonian translocations identified in a diagnostic laboratory in China |journal=PLoS ONE |volume=10 |issue=5 |pages=e0122647 |date=2015 |pmid=25932913 |pmc=4416705 |doi=10.1371/journal.pone.0122647 |url=}}</ref><ref name="pmid1831959">{{cite journal |vauthors=Petersen MB, Adelsberger PA, Schinzel AA, Binkert F, Hinkel GK, Antonarakis SE |title=Down syndrome due to de novo Robertsonian translocation t(14q;21q): DNA polymorphism analysis suggests that the origin of the extra 21q is maternal |journal=Am. J. Hum. Genet. |volume=49 |issue=3 |pages=529–36 |date=September 1991 |pmid=1831959 |pmc=1683126 |doi= |url=}}</ref> | ||
* '''Mosaicism''' | * '''Mosaicism''' | ||
** Post-fertilization mitotic error<ref name="pmid4257130">{{cite journal |vauthors=Hsu LY, Gertner M, Leiter E, Hirschhorn K |title=Paternal trisomy 21 mosaicism and Down's syndrome |journal=Am. J. Hum. Genet. |volume=23 |issue=6 |pages=592–601 |date=November 1971 |pmid=4257130 |pmc=1706744 |doi= |url=}}</ref><ref name="pmid12831601">{{cite journal |vauthors=Modi D, Berde P, Bhartiya D |title=Down syndrome: a study of chromosomal mosaicism |journal=Reprod. Biomed. Online |volume=6 |issue=4 |pages=499–503 |date=June 2003 |pmid=12831601 |doi= |url=}}</ref> | ** Post-[[fertilization]] [[mitotic]] error<ref name="pmid4257130">{{cite journal |vauthors=Hsu LY, Gertner M, Leiter E, Hirschhorn K |title=Paternal trisomy 21 mosaicism and Down's syndrome |journal=Am. J. Hum. Genet. |volume=23 |issue=6 |pages=592–601 |date=November 1971 |pmid=4257130 |pmc=1706744 |doi= |url=}}</ref><ref name="pmid12831601">{{cite journal |vauthors=Modi D, Berde P, Bhartiya D |title=Down syndrome: a study of chromosomal mosaicism |journal=Reprod. Biomed. Online |volume=6 |issue=4 |pages=499–503 |date=June 2003 |pmid=12831601 |doi= |url=}}</ref> | ||
''For a detailed description on the mechanisms leading to Down's syndrome,'' '''click [[Down syndrome pathophysiology|here]]''' | ''For a detailed description on the mechanisms leading to Down's syndrome,'' '''click [[Down syndrome pathophysiology|here]]''' | ||
Revision as of 23:36, 20 March 2018
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Down's syndrome (DS) is caused due to the presence of an extra 21st chromosome (triplication of chromosome 21). 95 percent of DS cases are due to meiotic non-disjunction during meiosis I. 4 percent of DS cases arise due to Robertsonian translocation and very rarely DS may be caused a post-fertilization mitotic error (mosaicism).
Causes
Down's syndrome is caused by triplication of chromosome 21 (trisomy 21). The aneuploidy may occur in three possible ways:
- Meiotic nondisjunction of homologous chromosomes
- From improper division of chromosomes during meiosis I or meiosis II. One gamete will end up with extra 21st chromosome.[1][2]
- Robertsonian translocation
- Individuals with normal number of chromosomes but an extra portion of 21st chromosome.[3][4][5]
- Mosaicism
- Post-fertilization mitotic error[6][7]
For a detailed description on the mechanisms leading to Down's syndrome, click here
References
- ↑ Antonarakis SE (March 1991). "Parental origin of the extra chromosome in trisomy 21 as indicated by analysis of DNA polymorphisms. Down Syndrome Collaborative Group". N. Engl. J. Med. 324 (13): 872–6. doi:10.1056/NEJM199103283241302. PMID 1825697.
- ↑ Antonarakis SE, Petersen MB, McInnis MG, Adelsberger PA, Schinzel AA, Binkert F, Pangalos C, Raoul O, Slaugenhaupt SA, Hafez M (March 1992). "The meiotic stage of nondisjunction in trisomy 21: determination by using DNA polymorphisms". Am. J. Hum. Genet. 50 (3): 544–50. PMC 1684265. PMID 1347192.
- ↑ Hook EB (October 1984). "Parental age and unbalanced Robertsonian translocations associated with Down syndrome and Patau syndrome: comparison with maternal and paternal age effects for 47, +21 and 47, +13". Ann. Hum. Genet. 48 (Pt 4): 313–25. PMID 6238567.
- ↑ Zhao WW, Wu M, Chen F, Jiang S, Su H, Liang J, Deng C, Hu C, Yu S (2015). "Robertsonian translocations: an overview of 872 Robertsonian translocations identified in a diagnostic laboratory in China". PLoS ONE. 10 (5): e0122647. doi:10.1371/journal.pone.0122647. PMC 4416705. PMID 25932913.
- ↑ Petersen MB, Adelsberger PA, Schinzel AA, Binkert F, Hinkel GK, Antonarakis SE (September 1991). "Down syndrome due to de novo Robertsonian translocation t(14q;21q): DNA polymorphism analysis suggests that the origin of the extra 21q is maternal". Am. J. Hum. Genet. 49 (3): 529–36. PMC 1683126. PMID 1831959.
- ↑ Hsu LY, Gertner M, Leiter E, Hirschhorn K (November 1971). "Paternal trisomy 21 mosaicism and Down's syndrome". Am. J. Hum. Genet. 23 (6): 592–601. PMC 1706744. PMID 4257130.
- ↑ Modi D, Berde P, Bhartiya D (June 2003). "Down syndrome: a study of chromosomal mosaicism". Reprod. Biomed. Online. 6 (4): 499–503. PMID 12831601.