Worton R G, Duff C, Campbell C E
Somatic Cell Genet. 1980 Mar;6(2):199-213. doi: 10.1007/BF01538796.
Segregation, defined as the reexpression of the recessive phenotype, has been examined in Chinese hamster cell hybrids heterozygous at the recessive emtr locus. Segregants were selected in emetine, and the role of chromosome loss in the segregation process was evaluated by detailed karyotype comparison of segregants with their hybrid parent. In emtr CHO x emt+ CHO hybrids (CHO is thought to be hemizygous at the emt locus), segregants were obtained at high frequency, and no consistent chromosome loss was found in the segregants. In hybrids made with Emtr CHO and wild-type lines other than CHO (CHW,CHL,V-79), where two wild-type alleles are thought to be present in the hybrid, segregants were obtained at much lower frequency, consistent with a two-step segregation process. These segregants revealed consistent loss of one chromosome 2 or deletion of a part of the long arm of a chromosome 2. Thus, one step in segregation seems to be chromosome loss while the other step must have a different mechanism, possibly the same mechanism that operates in the CHO x CHO hybrids. Two major conclusions can be drawn: (1) the emt gene maps to a hemizygous region of the long arm of a chromosome 2 in Chinese hamster, and (2) a segregation mechanism other than chromosome loss appears to operate with high efficiency in intraspecific hybrids.
分离现象，即隐性表型的再次表达，已在中国仓鼠细胞杂交体中进行了研究，这些杂交体在隐性的emtr位点为杂合状态。在吐根碱中筛选分离体，并通过对分离体与其杂交亲本进行详细的核型比较，评估染色体丢失在分离过程中的作用。在emtr CHO×emt+ CHO杂交体（人们认为CHO在emt位点为半合子）中，分离体高频出现，且在分离体中未发现一致的染色体丢失现象。在用Emtr CHO与除CHO外的野生型品系（CHW、CHL、V - 79）构建的杂交体中，人们认为杂交体中存在两个野生型等位基因，分离体出现的频率要低得多，这与两步分离过程一致。这些分离体显示出一致地丢失一条2号染色体或2号染色体长臂的一部分发生缺失。因此，分离的一个步骤似乎是染色体丢失，而另一个步骤必定有不同的机制，可能与在CHO×CHO杂交体中起作用的机制相同。可以得出两个主要结论：（1）emt基因定位于中国仓鼠2号染色体长臂的一个半合子区域，（2）除染色体丢失外的一种分离机制似乎在种内杂交体中高效起作用。
