Ikonen R S, Lindlöf M, Janas M O, Simola K O, Millington-Ward A, de la Chapelle A
Department of Pediatrics, University Central Hospital of Tampere, Finland.
Hum Genet. 1989 Oct;83(3):235-8. doi: 10.1007/BF00285163.
A family in which the proband showed phenotypic signs of both the Turner and Down syndromes was studied cytogenetically and with restriction fragment length polymorphisms. The proband's karyotype was 46,X,+21, showing double aneuploidy without any signs of mosaicism. The single X and one chromosome 21 were of paternal origin while two chromosome 21 were of maternal origin. The nondisjunction of chromosome 21 took place in maternal meiosis II. If it is assumed that the absence of mosaicism renders postzygotic mitotic loss of the X chromosome unlikely, then the X chromosome would have been lost in maternal meiosis I or II. Recombination had occurred between the nondisjoined chromosomes 21. We conclude that double nondisjunction took place in one patient and that asynapsis was not a prerequisite for the autosomal nondisjunction.
对一个先证者表现出特纳综合征和唐氏综合征表型特征的家庭进行了细胞遗传学和限制性片段长度多态性研究。先证者的核型为46,X,+21，显示双非整倍体，无任何嵌合体迹象。单条X染色体和一条21号染色体来自父方，而两条21号染色体来自母方。21号染色体的不分离发生在母方减数分裂II期。如果假设不存在嵌合体使得X染色体在合子后有丝分裂期丢失的可能性不大，那么X染色体可能在母方减数分裂I期或II期丢失。在未分离的21号染色体之间发生了重组。我们得出结论，在一名患者中发生了双不分离，并且联会紊乱不是常染色体不分离的先决条件。
