Searle A G, Beechey C V, de Boer P, de Rooij D G, Evans E P, Kirk M
Cytogenet Cell Genet. 1983;36(4):617-26. doi: 10.1159/000131985.
Is(7;1)40H was found in the daughter of a male mouse given spermatozoal X-irradiation. It is a non-inverted insertion of about half of chromosome 7 into chromosome 1, generating a long somatic marker chromosome. Breakpoints are in bands 1B, 7B1, and 7F1; linkage tests show that these breakpoints are about midway between fz and In on the 1, and 0.2 units distal to ru-2 and 12 units proximal to fr on the 7. Female carriers had litters of about one-third normal size and showed some decline in length of reproductive life. Males were sterile, with testis weights only 30% of normal and with abrupt cessation of spermatogenesis in pachytene at stage IV of the seminiferous epithelial cycle. Positive sex-vesicle contact with the insertional configuration was found in only 40% of pachytene spermatocytes, which suggested that other factors may be involved in the spermatogonial breakdown. In oocytes at metaphase I 76% of insertion configurations were multivalent, because of one or more chiasmata in the inserted segment, as were 79% of synaptonemal complex configurations in male pachytenes. Karyotyping at 12.5 to 14.5 days of gestation showed that all embryos with duplications of the inserted segment were exencephalic, and the only example of a corresponding deficiency was retarded. Analysis of the consequences of heterozygosity for the insertion shows that the insertion length should be correlated with the frequency of unbalanced offspring and thus with the amount of F1 lethality. The genetic length of 36 cM estimated in this way from data on liveborn offspring is in reasonable agreement with estimates from cytological measurements and meiotic configurations but rather higher than that from linkage tests.
在一只接受精子X射线照射的雄性小鼠的女儿中发现了Is(7;1)40H。它是约一半的7号染色体非倒位插入到1号染色体中，产生了一条长的体细胞标记染色体。断点位于1B、7B1和7F1带；连锁测试表明，这些断点在1号染色体上fz和In之间大约中间位置，在7号染色体上ru - 2远端0.2个单位处以及fr近端12个单位处。雌性携带者产仔数约为正常大小的三分之一，并且生殖寿命有所缩短。雄性不育，睾丸重量仅为正常的30%，在生精上皮周期IV期粗线期精子发生突然停止。仅在40%的粗线期精母细胞中发现了与插入构型的阳性性泡接触，这表明其他因素可能参与了精原细胞的破坏。在第一次减数分裂中期的卵母细胞中，76%的插入构型是多价的，这是因为插入片段中有一个或多个交叉，在雄性粗线期联会复合体构型中这一比例为79%。在妊娠12.5至14.5天进行核型分析表明，所有插入片段重复的胚胎都是无脑畸形的，唯一相应缺失的例子发育迟缓。对插入杂合性后果的分析表明，插入长度应与不平衡后代的频率相关，从而与F1致死率相关。根据活产后代数据以这种方式估计的36 cM的遗传长度与细胞学测量和减数分裂构型的估计结果合理一致，但比连锁测试的结果要高一些。
