Howell R T, McDermott A, Gardner A, Dickinson V
J Med Genet. 1984 Aug;21(4):310-4. doi: 10.1136/jmg.21.4.310.
An account is given of the cytogenetic investigations of a girl with Down's syndrome found to have a dicentric duplication of chromosome 21. This tandem type of rearrangement was interpreted as a recombinant derived from a single meiotic crossover between a maternal ring 21 and its normal homologue. A population of cells was also found in which breakage of the dicentric resulted in a chromosome 21 with a small terminal deletion. The mother and the proband's younger brother, who was also a ring 21 heterozygote, were both clinically normal.
报告了一名患有唐氏综合征的女孩的细胞遗传学研究情况，发现其21号染色体存在双着丝粒重复。这种串联型重排被解释为源自母源21号环状染色体与其正常同源染色体之间的单个减数分裂交叉产生的重组体。还发现了一群细胞，其中双着丝粒的断裂导致一条21号染色体带有小的末端缺失。母亲以及先证者的弟弟（也是21号环状染色体杂合子）临床均正常。
