Rockmill B, Fogel S
Department of Genetics, University of California, Berkeley 94720.
Genetics. 1988 Jun;119(2):261-72. doi: 10.1093/genetics/119.2.261.
Mutants at a newly identified locus, DIS1 (disjunction), were detected by screening for mutants that generate aneuploid spores (chromosome VIII disomes) at an increased frequency. Strains carrying the partially dominant alleles, DIS1-1 or DIS1-2, generate disomes at rates up to 100 times the background level. Mitotic nondisjunction is also increased 10- to 50-fold over background. Half-tetrad analysis of disomes for a marked interval on chromosome VIII yields wild-type map distances, indicating that a general recombination deficiency is not the cause of nondisjunction. Meiotic nondisjunction in DIS1 mutants is not chromosome specific; 5% of the spores disomic for chromosome VIII are also disomic for chromosome III. Although only one disomic spore is found per exceptional ascus most of the disomes appear to be generated in the first meiotic division because recovered chromosome VIII disomes contain mostly nonsister chromosomes. We propose that disome generation in the DIS1 mutants results from precocious separation of sister centromeres.
通过筛选以增加频率产生非整倍体孢子（第八条染色体双体）的突变体，检测到一个新确定位点DIS1（分离）处的突变体。携带部分显性等位基因DIS1-1或DIS1-2的菌株产生双体的频率高达背景水平的100倍。有丝分裂不分离也比背景增加了10到50倍。对第八条染色体上一个标记区间的双体进行半四分体分析，得到野生型图谱距离，表明一般的重组缺陷不是不分离的原因。DIS1突变体中的减数分裂不分离不是染色体特异性的；第八条染色体双体的5%的孢子也是第三条染色体双体。虽然每个异常子囊中只发现一个双体孢子，但大多数双体似乎是在第一次减数分裂中产生的，因为回收的第八条染色体双体大多包含非姐妹染色体。我们提出，DIS1突变体中双体的产生是由于姐妹着丝粒的过早分离。
