An endomitotic effect of a cell cycle mutation of Saccharomyces cerevisiae.
An endomitotic effect of a cell cycle mutation of Saccharomyces cerevisiae.
复制标题
酿酒酵母细胞周期突变的内有丝分裂效应。
作者：
D. Schild;H. Ananthaswamy;R. Mortimer
酿酒酵母的一个隐性温度敏感突变已经被分离出来，并被证明在单倍体和二倍体中都能引起倍性增加。遗传分析表明，携带突变的菌株是aa二倍体，尽管已经对a单倍体菌株进行了MNNG诱变。当突变株与α二倍体杂交并产生四倍体时，遗传分析和DNA测量表明，该四倍体的一些减数分裂后代本身就是四倍体，而不是四倍体减数分裂所预期的二倍体。这些四倍体继续产生四倍体减数分裂后代的能力被跟踪了四代。单倍体倍性增加的原因被排除在外；对大约32-细胞期的孢子克隆的目测系谱分析没有发现任何合子，二倍化的单倍体保留了交配型。另一轮减数分裂DNA合成也被考虑和排除。结果表明，四倍体的发生与孢子形成温度无关，而与萌发温度和孢子生长有关。当孢子萌发并在30度生长时，倍性增加，但在23度时不出现倍性增加。单倍体的形成和生长在23℃下进行两个周期，单倍体在30℃下生长24小时内二倍体。对36度孵育的单倍体细胞的肉眼观察显示，影响核分裂的突变具有细胞分裂周期的表型特征；互补分析表明，该突变cdc31-2与Hartwell等人分离的突变cdc31-1等位。(1973)，并被描述为在核分裂后期引起温度敏感型逮捕。Cdc31-2在杂合二倍体中的分离比例为2：2，为非着丝粒连锁基因。
A recessive temperature-sensitive mutation of Saccharomyces cerevisiae has been isolated and shown to cause an increase in ploidy in both haploids and diploids. Genetic analysis revealed that the strain carrying the mutation was an aa diploid, although MNNG mutagenesis had been done on an a haploid strain. When the mutant strain was crossed with an alpha alpha diploid and the resultant tetraploid sporulated, some of the meiotic progeny of this tetraploid were themselves tetraploid, as shown by both genetic analysis and DNA measurements, instead of diploid as expected of tetraploid meiosis. The ability of these tetraploids to continue to produce tetraploid meiotic progeny was followed for four generations. Homothallism was excluded as a cause of the increase in ploidy; visual pedigree analysis of spore clones to about the 32-cell stage failed to reveal any zygotes, and haploids that diploidized retained their mating type. An extra round of meiotic DNA synthesis was also considered and excluded. It was found that tetraploidization was independent of sporulation temperature, but was dependent on the temperature of germination and the growth of the spores. Increase in ploidy occurred when the spores were germinated and grown at 30 degrees, but did not occur at 23 degrees. Two cycles of sporulation and growth at 23 degrees resulted in haploids, which were shown to diploidize within 24 hr when grown at 30 degrees. Visual observation of the haploid cells incubated at 36 degrees revealed a cell-division-cycle phenotype characteristic of mutations that affect nuclear division; complementation analysis demonstrated that the mutation, cdc31-2, is allelic to cdc31-1, a mutation isolated by Hartwell et al. (1973) and characterized as causing a temperature-sensitive arrest during late nuclear division. The segregation of cdc31-2 in heterozygous diploids was 2:2 and characteristic of a noncentromere-linked gene.