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Down syndrome or Down's syndrome, [12] also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. [3] It is usually associated with developmental delays, mild to moderate intellectual disability , and characteristic physical features.
Children with Down syndrome or developmental coordination disorder are late to reach major motor skills milestones like sucking, grasping, rolling, sitting up and walking, talking. Children with Down syndrome sometimes have heart problems, frequent ear infections, hypotonia, or undeveloped muscle mass.
Mosaic Down syndrome: Only some cells in the person have an extra copy of chromosome 21. This genetic cause is considered rare. This genetic cause is considered rare.
Developmental symptoms, meanwhile, may include a short attention span, impulsive behavior, slow learning and delayed speech development. Not every child with Down syndrome will display each of ...
There is considerable variability in the fraction of cells with trisomy 21, both as a whole and tissue-by-tissue. This is the cause of 1–2% of the observed Down syndromes. [4] There is evidence that mosaic Down syndrome may produce less developmental delay, on average, than full trisomy 21. [8]
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While applying the Bayley Scales of Infant Development (BSID-II), it was found that scales may lead to under-estimates of cognitive abilities in infants with Down syndrome. [7] Researchers excluded a number of items that implicated language, motor , attentional and social functioning from the original measures the modified form was administered ...
Down syndrome is a genetic condition in which people are born with an extra copy of chromosome 21. This extra copy affects the development of the body and brain, causing a range of physical and mental impairments for the individual. Fragile X syndrome, most frequent among males, is thought to cause autism and intellectual disability.