Lurie I W, Presman H, Lazjuk G I
J Genet Hum. 1978 Dec;26(4):385-92.
The analysis of 206 families with reciprocal translocations revealed thanks to a patient who was a carrier of an unbalanced translocation demonstrated the risk of a child suffering from the disease at about 16.4%, in the case of a meiotic segregation 2 : 2. In the case of translocation with meiotic segregation 3 : 1, the risk is much less, i.e. 7.6% for female carriers and significantly less than 3/83 for male carriers. It is extremely important to take this difference into account when evaluating the risks during genetic counselling. On the other hand, the freqeuncy of spontaneous abortions is practically the same for carriers of translocations with these two types of segregation and rises to nearly 23%; i.e. the postzygotic selection influences, to the same degree, zygotes with one chromosome too many, one two few, and zygotes with 46 chromosomes, but of which one has a defect or an excess of genetic material. Such selection depends rather on an interaction between the abnormal genome of the zygote (embryo) and the genome of the mother, whilst the prezygotic selection operates against the gametes having one chromosome too many or one too few. A large asymmetry in the length of the exchanged fragments could be one of the causes of the 3 : 1 segregation. This is proved by a more frequent participation (48/60) of the acrocentric chromosomes in the translocations with segregation 3 : 1. On the other hand, in translocations with segregation 2 : 2, acrocentrics are found much more rarely (66/146).
对206个相互易位家族的分析表明，由于一名不平衡易位携带者患者，在减数分裂分离为2:2的情况下，孩子患该病的风险约为16.4%。在减数分裂分离为3:1的易位情况下，风险要小得多，即女性携带者为7.6%，男性携带者明显低于3/83。在遗传咨询中评估风险时考虑到这种差异极为重要。另一方面，这两种分离类型的易位携带者的自然流产频率实际上是相同的，几乎达到23%；也就是说，合子后选择对染色体过多、过少的合子以及有46条染色体但其中一条有遗传物质缺陷或过多的合子的影响程度相同。这种选择更多地取决于合子（胚胎）的异常基因组与母亲基因组之间的相互作用，而合子前选择则作用于染色体过多或过少的配子。交换片段长度的巨大不对称可能是3:1分离的原因之一。这一点由近端着丝粒染色体在3:1分离的易位中更频繁参与（48/60）得到证明。另一方面，在2:2分离的易位中，近端着丝粒染色体则极为罕见（66/146）。
