Borts R H, Lichten M, Haber J E
Genetics. 1986 Jul;113(3):551-67. doi: 10.1093/genetics/113.3.551.
We have developed a method by which the extent of physical exchange of DNA molecules can be determined throughout meiosis in the yeast Saccharomyces cerevisiae. We have used this technique to analyze the effect of five meiosis-defective mutations (rad6, rad50, rad52, rad57 and spo11) on the physical exchange of DNA molecules. In the same experiments, we have also measured other meiotic parameters, such as premeiotic DNA synthesis, commitment to intragenic recombination, haploidization, ascus formation, and viability. rad50 and spo11 diploids make an undetectable amount of physically recombined DNA and less than 1% of wild-type levels of viable intragenic recombinants. In contrast, diploids homozygous for rad52, rad6 or rad57 all yield significant amounts of novel restriction fragments which arise by recombination. rad57 diploids make nearly wild-type levels of the recombined restriction fragments, although they produce less than 10% of the wild-type levels of viable intragenic recombinants. rad52 strains are also capable of a significant (33%) amount of exchange of DNA molecules, but make less than 1% of wild-type levels of viable intragenic recombinants. rad6 diploids are also capable of undergoing a high level of exchange, as measured by the appearance of the recombined restriction fragment. In addition, rad6 diploids show an unusual allele- or locus-specific variability in the level of viable intragenic recombinants produced. Although rad6 diploids produce no viable spores, they are able to complete a significant amount of haploidization upon return to vegetative growth conditions.
我们开发了一种方法，通过该方法可以确定酿酒酵母减数分裂过程中DNA分子的物理交换程度。我们已使用此技术分析了五个减数分裂缺陷突变（rad6、rad50、rad52、rad57和spo11）对DNA分子物理交换的影响。在相同的实验中，我们还测量了其他减数分裂参数，如减数分裂前DNA合成、基因内重组的发生、单倍体化、子囊形成和活力。rad50和spo11二倍体产生的物理重组DNA量无法检测到，并且产生的有活力的基因内重组体水平不到野生型水平的1%。相比之下，rad52、rad6或rad57纯合的二倍体均产生大量通过重组产生的新型限制性片段。rad57二倍体产生的重组限制性片段水平接近野生型，尽管它们产生的有活力的基因内重组体水平不到野生型水平的10%。rad52菌株也能够进行显著（33%）的DNA分子交换，但产生的有活力的基因内重组体水平不到野生型水平的1%。通过重组限制性片段的出现来衡量，rad6二倍体也能够进行高水平的交换。此外，rad6二倍体在产生的有活力的基因内重组体水平上表现出不寻常的等位基因或位点特异性变异性。尽管rad6二倍体不产生有活力的孢子，但它们在恢复到营养生长条件时能够完成大量的单倍体化。
