Sherman S L, Takaesu N, Freeman S B, Grantham M, Phillips C, Blackston R D, Jacobs P A, Cockwell A E, Freeman V, Uchida I
Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322.
Am J Hum Genet. 1991 Sep;49(3):608-20.
To assess the association between recombination and nondisjunction of chromosome 21, we analyzed cytogenetic and DNA markers in 104 trisomy 21 individuals and their parents. Our DNA marker studies of parental origin were informative in 100 cases, with the overwhelming majority (94) being maternal in origin. This value is significantly higher than the 75%-80% maternal nondisjunction rate typically observed in cytogenetic studies of trisomy 21 and illustrates the increased accuracy of the molecular approach. Using the maternally derived cases and probing at 19 polymorphic sites on chromosome 21, we created a genetic map that spans most of the long arm of chromosome 21. The map was significantly shorter than the normal female linkage map, indicating that absence of pairing and/or recombination contributes to nondisjunction in a substantial proportion of cases of trisomy 21.
为评估21号染色体的重组与不分离之间的关联，我们分析了104例21三体个体及其父母的细胞遗传学和DNA标记。我们对亲本来源的DNA标记研究在100例中提供了信息，绝大多数（94例）起源于母亲。该值显著高于21三体细胞遗传学研究中通常观察到的75%-80%的母亲不分离率，说明了分子方法的准确性提高。利用母源病例并在21号染色体上的19个多态性位点进行探测，我们构建了一个覆盖21号染色体大部分长臂的遗传图谱。该图谱明显短于正常女性连锁图谱，表明配对和/或重组的缺失在相当比例的21三体病例中导致了不分离。
