21三体是儿童最常见的染色体异常疾病,也是智力低下最常见的遗传因素,鉴定其额外染色体的来源有助于阐明该病的发生机理。过去20年主要根据染色体核型分析,由21号染色体短臂的形态变化推测额外染色体的来源,发现母源性者约占80%,父源性占20%。然而细胞学受形态变异所提供信息多少的限制,且评价带有主观性。 Trisomy is the most common chromosomal abnormality in children and is also the most common genetic predisposition for mental retardation. Identifying the source of extra chromosomes can help clarify the pathogenesis of the disease. Based on the karyotype analysis of the chromosomes in the past 20 years, the extra chromosomes were deduced from the morphological changes of the short arm of chromosome 21 and found that 80% of maternally derived and 20% of paternal originated. However, cytology is limited by the amount of information provided by morphological variation and is subjective.