Campbell D A, Fogel S, Lusnak K
Genetics. 1975 Mar;79(3):383-96. doi: 10.1093/genetics/79.3.383.
Experiments designed to characterize the incidence of mitotic chromosome loss in a yeast disomic haploid were performed; The selective methods employed utulize the non-mating property of strains disomic for linkage group III and heterozygous at the mating type locus. The principal findings are: (1) The grequency of spontaneous chromosome loss in the disome is of the order 10- minus 4 per cell; this value approximates the frequency in the same population of spontaneous mitotic exchange resulting in homozygosity at the mating type locus. (2) The recovered diploids are pure clones, and thus represent unique events in the disomic haploid. (3) Of the euploid chromosomes recovered after events leading to chromosome loss, approximately 90% retain the parental marker configuration expected from segregation alone; however, the remainder are recombinant for marker genes, and are the result of mitotic exchanges in the disome, especially in regions near the centromere. The recombinant proportion significantly exceeds that expected if chromosome loss and mitotic exchange in the disome were independent events. The data are consistent with a model proposing mitotic nondisjunction as the event responsible for chromosome loss in the disomic haploid.
开展了旨在表征酵母二体单倍体中有丝分裂染色体丢失发生率的实验；所采用的选择方法利用了第III连锁群二体且交配型位点杂合的菌株的非交配特性。主要发现如下：(1) 二体中自发染色体丢失的频率约为每细胞10的负4次方；该值近似于同一群体中导致交配型位点纯合的自发有丝分裂交换的频率。(2) 回收的二倍体是纯克隆，因此代表二体单倍体中的独特事件。(3) 在导致染色体丢失的事件后回收的整倍体染色体中，约90%保留了仅由分离预期的亲本标记构型；然而，其余的是标记基因的重组体，是二体中有丝分裂交换的结果，尤其是在着丝粒附近区域。如果二体中的染色体丢失和有丝分裂交换是独立事件，那么重组比例显著超过预期。这些数据与一个提出有丝分裂不分离是二体单倍体中染色体丢失原因的模型一致。
