Down Syndrome
Down syndrome is a genetic condition that occurs when a person has an extra copy of all or part of chromosome 21. This additional genetic material affects physical development, learning, and health. It is present from birth and is one of the most common chromosomal conditions.
Types
There are three main types:
Trisomy 21 (about 95% of cases): Every cell has an extra chromosome 21.
Translocation Down syndrome (about 3–4%): Extra chromosome 21 material is attached to another chromosome.
Mosaic Down syndrome (about 1–2%): Only some cells have the extra chromosome, so features and effects may be milder.
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