Down Syndrome: Difference between revisions
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Down Syndrome is a condition caused by [[Trisomy 21|trisomy 21]] due to [[Non disjunction|nondisjunction]] in [[Meiosis|meiosis]]. As a result, instead of normal 46 chromosomes, an affected person will have 47 chromosomes. Nondisjunction of the chromosome number 21 normally occurs in the gamete of the ovum of the mother in her forties. Down syndrome also occurs due to an unusual chromosome structure but at a very small percentage. The similar [[Phenotype|phenotypic]] feature of people with Down Syndrome is that they have broad and flat heads and flattened noses. Affected people have lower intellectual capacity and defective health with a shortened life expectancy which is less than 50 years. | Down Syndrome is a condition caused by [[Trisomy 21|trisomy 21]] due to [[Non disjunction|nondisjunction]] in [[Meiosis|meiosis]]. As a result, instead of normal 46 chromosomes, an affected person will have 47 chromosomes. Nondisjunction of the chromosome number 21 normally occurs in the gamete of the ovum of the mother in her forties. Down syndrome also occurs due to an unusual chromosome structure but at a very small percentage. The similar [[Phenotype|phenotypic]] feature of people with Down Syndrome is that they have broad and flat heads and flattened noses. Affected people have lower intellectual capacity and defective health with a shortened life expectancy which is less than 50 years. | ||
Reference: Hartl, D.L., Jones, E.W. (2009) Genetics: Analysis of Genes and Genomes, United States of America: Jones and Bartlet | |||
Revision as of 22:16, 29 November 2012
Down Syndrome is a condition caused by trisomy 21 due to nondisjunction in meiosis. As a result, instead of normal 46 chromosomes, an affected person will have 47 chromosomes. Nondisjunction of the chromosome number 21 normally occurs in the gamete of the ovum of the mother in her forties. Down syndrome also occurs due to an unusual chromosome structure but at a very small percentage. The similar phenotypic feature of people with Down Syndrome is that they have broad and flat heads and flattened noses. Affected people have lower intellectual capacity and defective health with a shortened life expectancy which is less than 50 years.
Reference: Hartl, D.L., Jones, E.W. (2009) Genetics: Analysis of Genes and Genomes, United States of America: Jones and Bartlet