Down syndrome - Wikipedia
https://en.m.wikipedia.org/wiki/Down_syndrome
Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with developmental delays, mild to moderate intellectual disability, and characteristic physical features. There are three types of Down syndrome, all with the same features: Trisomy 21, the most common type; Mosaic Down syndrome, and Transloca… Usual onset: Mostly at conception, rarely …
Usual onset: Mostly at conception, rarely …
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