GENETIC CONTROL OF SISTER CHROMATID EXCHANGE IN YEAST

为了试图了解遗传控制和分子机制， 酿酒酵母姊妹染色单体交换突变体 姐妹染色单体交换水平升高的人。 这些突变体是在一个菌株中分离出来的， HIS 3基因，并含有两个截短拷贝的HIS 3基因 整合在染色体IV的着丝粒附近;不等姐妹染色单体 HIS 3基因同源区域之间的交换可以恢复 功能基因 姐妹染色单体交换增加的突变体是 根据其形成HIS+原养型的能力增加进行鉴定 与未诱变的对照克隆相比。 三个突变体（esr 1，esr 2， ESR 3）已经被广泛表征。 每一个突变体 就像一个单一的孟德尔基因座 esr 1和esr 2具有升高的 有丝分裂基因转换 克隆esr 1，esr 2， 和ESR 3基因互补。 使用相同的系统，已知RAD，突变，减数分裂和DNA的影响 对SCR上的破坏剂进行了测量。 我们也在确定 不同修复基因对SCR的影响。

In an attempt to understand the genetic control and molecular mechanisms of sister chromatid exchange in the yeast Saccharomyces cerevisiae, mutants with elevated levels of sister chromatid exchange have been isolated. These mutants were isolated in a strain that is deleted for the resident HIS3 gene and that contains two truncated copies of the HIS3 genes integrated near the centromere of chromosome IV; unequal sister chromatid exchange between homologous regions of the HIS3 gene can restore the functional gene. Mutants elevated for sister chromatid exchange were identified based on their increased ability to form HIS+ prototrophs compared to the control unmutagenized clones. Three mutants (esr1, esr2, esr3) have been characterized extensively. Each of these mutants behaves like a single Mendelian locus. esr1 and esr2 have elevated levels of mitotic gene conversion. Experiments are underway to clone the esr1, esr2, and esr3 genes by complementation. Using the same system, effects of know RAD, mutations, meiosis, and DNA damaging agents on SCR have been measured. We are also determining the influence of various repair genes on SCR.