Engel E, DeLozier-Blanchet C D
University Institute of Medical Genetics, Geneva, Switzerland.
Am J Med Genet. 1991 Sep 15;40(4):432-9. doi: 10.1002/ajmg.1320400411.
The concept of uniparental disomy--the presence of a chromosome pair derived solely from one parent in a diploid offspring--was introduced in 1980 as a probable consequence of the high rate of germ cell aneuploidy in man, and has now been convincingly demonstrated through molecular analyses in several families. A most likely mechanism for the production of uniparental disomy is the chance reunion, and complementation, of 2 gametes aneuploid for the same chromosome member; uniparental disomy could also occur through other mechanisms including postzygotic non-segregation in a trisomic conceptus. Uniparental disomy may result in isodisomy, i.e., homozygosity of a series of contiguous alleles in a pair of homologues. The presence and degree of isodisomy in an offspring depend in turn on the occurrence, timing, and extent of the meiotic recombination that had occurred in the chromosome pair of the disomic gamete involved. Uniparental disomy with or without isodisomy can explain a number of unusual observations, such as the unexpected pattern of transmission of a genetic disorder. The two may be associated with an imprinting effect to produce pathological phenotypes, as has been observed in the mouse, and may be the basis for a number of syndromes of as yet unclear cause. The evidence for uniparental disomy, isodisomy, and imprinting in man is reviewed, and strategies for their detection presented.
单亲二体的概念——即二倍体后代中某对染色体完全来自父母一方——于1980年被提出，被认为是人类生殖细胞非整倍体发生率高的一个可能结果，目前已通过对多个家族的分子分析得到了令人信服的证实。产生单亲二体最可能的机制是两个对同一染色体成员呈非整倍体的配子偶然重聚并互补；单亲二体也可能通过其他机制发生，包括三体受精卵中的合子后不分离。单亲二体可能导致同二体，即一对同源染色体中一系列相邻等位基因的纯合性。后代中同二体的存在及程度反过来又取决于所涉及的二体配子染色体对中减数分裂重组的发生、时间及程度。有无同二体的单亲二体都能解释一些异常现象，比如遗传疾病的意外传递模式。两者可能与印记效应相关，从而产生病理表型，正如在小鼠中所观察到的那样，并且可能是一些病因尚不清楚的综合征的基础。本文综述了人类单亲二体、同二体及印记现象的证据，并介绍了检测它们的策略。
