Down syndrome causes: Difference between revisions
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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 (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. | ** 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> | ||
* '''Robertsonian translocation''' | * '''Robertsonian translocation''' | ||
** Individuals with normal number of chromosomes but an extra portion of 21st chromosome. | ** Individuals with normal number of chromosomes but an extra portion of 21st chromosome. | ||
* '''Mosaicism''' | * '''Mosaicism''' | ||
** Post-fertilization mitotic error | ** Post-fertilization mitotic error | ||
For a detailed description on the mechanisms leading to Down's syndrome, click [[Down syndrome pathophysiology|here]] | |||
==References== | ==References== | ||
Revision as of 23:27, 20 March 2018
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
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
- Robertsonian translocation
- Individuals with normal number of chromosomes but an extra portion of 21st chromosome.
- Mosaicism
- Post-fertilization mitotic error
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.