Down Syndrome - Research Article from Macmillan Science Library: Genetics

This encyclopedia article consists of approximately 4 pages of information about Down Syndrome.
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Down Syndrome

Down syndrome, also called trisomy 21, is the single most common genetic cause of moderate mental retardation. It occurs in about one of every eight hundred live births. It is caused by the inheritance of an extra copy of chromosome 21. The condition was named after an English physician, J. Langdon Down, who in 1866 published the first report describing patients with similar facial features and mental retardation. The chromosomal basis of Down syndrome was not determined until nearly a century later.

Clinical Features

Down syndrome is associated with a characteristic physical appearance, mental retardation, and specific birth defects or health conditions. The facial features, in addition to low muscle tone (called hypotonia), are often the first signs that alert a physician to a potential diagnosis of Down syndrome. These features include an up-slant of the outer corners of the eyes, small skin folds over the inner corners of...

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This section contains 1,062 words
(approx. 4 pages at 300 words per page)
Buy the Down Syndrome Encyclopedia Article
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Macmillan Science Library: Genetics
Down Syndrome from Macmillan Science Library: Genetics. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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