James R S, Ellis K, Pettay D, Jacobs P A
Wessex Regional Genetics Laboratory, Salisbury District Hospital, Wiltshire, UK.
Eur J Hum Genet. 1998 May-Jun;6(3):207-12. doi: 10.1038/sj.ejhg.5200178.
We studied four families each with three trisomy 21 conceptions. In two of the families the trisomy 21 conceptions all occurred when the mothers were under 35 years of age and in the other two families they all occurred when the mothers were over 35 years of age. Cytogenetic studies showed low level mosaic trisomy 21 in the two younger mothers, but not in the two older. In the three families tested using molecular techniques the results were consistent with the additional chromosome 21 in the trisomic conceptuses being maternally derived. Novel alleles were detected in the trisomic offspring of one of the younger mothers, demonstrating that the mother had been conceived as a trisomy with three different chromosomes 21. Therefore the multiple trisomy 21 pregnancies in the two younger mothers resulted from maternal trisomy 21 mosaicism, but may have been due to chance in the older mothers.
我们研究了四个家庭，每个家庭都有三次21三体妊娠。在其中两个家庭中，21三体妊娠均发生在母亲年龄小于35岁时，而在另外两个家庭中，均发生在母亲年龄大于35岁时。细胞遗传学研究显示，两位年轻母亲存在低水平的21三体嵌合体，但两位年长母亲则没有。在使用分子技术检测的三个家庭中，结果表明三体妊娠中额外的21号染色体来自母亲。在一位年轻母亲的三体后代中检测到了新的等位基因，表明这位母亲自身也是一个具有三条不同21号染色体的三体。因此，两位年轻母亲的多次21三体妊娠是由母亲的21三体嵌合体导致的，但年长母亲的情况可能是偶然因素所致。
