Analysis of the mechanism of chromosome-DNA length polymorphism and aplication to the gene amplification in yeast.

酿酒酵母MT98a-3d的第三号染色体DNA长度为450kbp，而普通菌株为350kbp。从该菌株衍生的孢子克隆中，三号染色体DNA长度的多态现象出现频率很高。限制性内切酶分析和遗传分析表明，450kbpIII染色体DNA含有约100kbp的过量DNA片段，THR4基因和HMR基因位于该DNA片段上。结果表明，该多态性是由减数分裂中姐妹染色质之间重复序列的不等交换(S)所致。我们计划利用这种染色体DNA长度多态性来扩增酵母染色体上的有用基因。

The length of chromosome III DNA of the strain of Saccharomyces cerevisiae, MT98a-3D, is 450 kbp, in contrast with the value of 350 kbp of ordinary strains. The DNA-length polymorophism of chromosome-III occur at a high frequency in spore clones derived from this strain. Restriction enzyme analyses and genetic analyses showed that the 450 kbp chromosome III DNA contains an excessive DNA fragment of about 100 kbp, on which the region from THR4 gene to HMR gene are located. It is indicated that the polymorphism is generated by unequal crossing over(s) at duplicated DNA sequences between sister chroinatids at meiosis. We planed to use this chromosome-DNA length polymorphism to the amplification of usefull genes on the chromosome in yeast.