Brahe C, Tassone F, Moscetti A, Millington-Ward A, Bova R, Serra A
Institute of Human Genetics, A. Gemelli School of Medicine, Rome, Italy.
Am J Med Genet Suppl. 1990;7:125-8. doi: 10.1002/ajmg.1320370725.
The parental origin of the extra chromosome 21 (or extra 21q) was determined in seven informative families with a Down syndrome (DS) child by using molecular polymorphisms. Five DS patients had regular trisomy, one a de novo 14/21 translocation and another a de novo 21/21 translocation or isochromosome 21q. In four families with regular trisomy, the extra chromosome was of maternal origin, and in one family it was paternally derived. In the two families with a de novo aberration, both the 14/21 translocation and 21/21 rearrangement originated during maternal meiosis. For a better evaluation of the stage of meiotic error and the occurrence of crossovers between nondisjoined chromosomes, the regional map position of four of the nine informative DNA markers, used in this study, was refined, leading to useful localizations in both centromeric and distal regions. Recombination events were found in two families with regular trisomy, one occurring between chromosomes 21 that failed to disjoin at maternal meiosis I, the other prior to a paternal meiosis II nondisjunction.
通过使用分子多态性，在7个有唐氏综合征（DS）患儿的信息丰富的家庭中确定了额外的21号染色体（或额外的21q）的亲本来源。5名DS患者为典型三体，1名是新发的14/21易位，另1名是新发的21/21易位或21号等臂染色体。在4个典型三体家庭中，额外的染色体来自母方，在1个家庭中来自父方。在2个新发畸变家庭中，14/21易位和21/21重排均发生在母方减数分裂期间。为了更好地评估减数分裂错误的阶段以及不分离染色体之间交叉互换的发生情况，对本研究中使用的9个信息性DNA标记中的4个进行了区域图谱定位的优化，从而在着丝粒区域和远端区域都得到了有用的定位。在2个典型三体家庭中发现了重组事件，1个发生在母方减数分裂I时未分离的21号染色体之间，另1个发生在父方减数分裂II不分离之前。
