Caused by the abnormality of chromosome 21, Down syndrome is the most common chromosomal disease as well as one of the most frequent known genetic causes of mental retardation.
唐氏综合症由人体21号染色体病变引起。它是最常见的染色体疾病，也是最主要的导致智力落后的基因病变。
Caused by the abnormality of chromosome 21, Down syndrome is the most common chromosomal disease as well as one of the most frequent known genetic causes of mental retardation.
唐氏综合症由人体21号染色体病变引起。它是最常见的染色体疾病，也是最主要的导致智力落后的基因病变。
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