Stene J, Stengel-Rutkowski S
Ann Hum Genet. 1982 Jan 1;46(1):41-74. doi: 10.1111/j.1469-1809.1982.tb00694.x.
An analysis of genetic risks for reciprocal translocations is given. Data from translocation families, ascertained through unbalanced offspring with trisomy 9p, 10p and 12p, were taken from the literature. The translocations were specified according to (1) the type of trisomy, (2) the degree of resulting chromosomal imbalance (partial short arm trisomies, complete short arm trisomies, complete short arm trisomies including long arm segments) and (3) the type of disjunction (2:2 or 3:1) and segregation (adjacent-1, adjacent-2; tertiary trisomy, interchange trisomy). The risks for unbalanced liveborn offspring were high for translocations leading to partial short arm trisomies through 2:2 disjunction and adjacent-1 segregation (25-29%). They were lower for translocations leading to complete short arm trisomies through the same disjunction/segregation mechanism (5-17%). Low risks were obtained for translocations, leading through 3:1 disjunction to unbalanced offspring (about 2%). For 2:2 disjunction and adjacent-2 segregation and for 3:1 disjunction the risk is significantly lower for male than for female carriers.--The frequency of balanced karyotypes compared with normal karyotypes deviated among the phenotypically normal offspring of parental carriers from the theoretical 1:1 ratio, both for translocations ascertained through trisomy 12p and trisomy 10p.--It was demonstrated that the genetic risk for reciprocal translocations depends exclusively on (1) the degree of possibly resulting genetic imbalance and (2) the probability of the disjunction/segregation mechanism leading to this type of imbalance. Both factors can be predicted from the position of breakpoints.--The precision of breakpoint localizations and its impact on the risk estimation are also considered.--Finally, general rules for genetic counselling of families with reciprocal translocations are indicated.
本文对相互易位的遗传风险进行了分析。通过9号染色体短臂、10号染色体短臂和12号染色体短臂三体的不平衡后代确定的易位家系数据来自文献。易位根据以下标准进行分类：(1)三体类型；(2)导致的染色体不平衡程度（部分短臂三体、完整短臂三体、包括长臂片段的完整短臂三体）；(3)分离类型（2:2或3:1）和分离方式（邻位-1、邻位-2；三级三体、相互易位三体）。通过2:2分离和邻位-1分离导致部分短臂三体的易位，其不平衡活产后代的风险较高（25%-29%）。通过相同分离/分离机制导致完整短臂三体的易位，其风险较低（5%-17%）。通过3:1分离导致不平衡后代的易位风险较低（约2%）。对于2:2分离和邻位-2分离以及3:1分离，男性携带者的风险显著低于女性携带者。——在通过12号染色体短臂三体和10号染色体短臂三体确定的易位中，亲代携带者表型正常的后代中，平衡核型与正常核型的频率偏离了理论上的1:1比例。——结果表明，相互易位的遗传风险仅取决于：(1)可能导致的遗传不平衡程度；(2)导致这种不平衡类型的分离/分离机制的概率。这两个因素都可以从断点位置预测。——还考虑了断点定位的精度及其对风险估计的影响。——最后，指出了相互易位家系遗传咨询的一般规则。
