Ds contributes to about 30 of all moderate tosevere

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Unformatted text preview: with short fingers. •  Low muscle tone. •  Down syndrome always involves some degree of mental retardation, from mild to severe, with IQ ranging between 30 and 70. DS contributes to about 30% of all moderate-tosevere cases of mental retardation. •  75% of Down syndrome individuals over 60 yrs of age develop Alzheimer-like symptoms. http://www.youtube.com/watch?v=bEVkbuooXo4&feature=related 1.22 min Down Syndrome (Trisomy 21) cytogenetics, a chromosome "spread" In 1959, the French geneEcist Jerome Lejeune showed that DS is associated with an extra chromosome 21 The main cause of Down syndrome is a meiotic non-disjunction Tris...
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