Clark S H, Hilliker A J, Chovnick A
Department of Molecular and Cell Biology, University of Connecticut, Storrs 06268.
Genetics. 1988 Feb;118(2):261-6. doi: 10.1093/genetics/118.2.261.
This report presents the results of a recombination experiment designed to question the existence of special sites for the initiation or termination of a recombination heteroduplex within the region of the rosy locus. Intragenic recombination events were monitored between two physically separated rosy mutant alleles ry301 and ry2 utilizing DNA restriction site polymorphisms as genetic markers. Both ry301 and ry2 are known from previous studies to be associated with gene conversion frequencies an order of magnitude lower than single site mutations. The mutations are associated with large, well defined insertions located as internal sites within the locus in prior intragenic mapping studies. On the molecular map, they represent large insertions approximately 2.7 kb apart in the second and third exons, respectively, of the XDH coding region. The present study monitors intragenic recombination in a mutant heterozygous genotype in which DNA homology is disrupted by these large discontinuities, greater than the region of DNA homology and flanking both sides of the locus. If initiation/or termination requires separate sites at either end of the locus, then intragenic recombination within the rosy locus of the heterozygote should be eliminated. Contrary to expectation, significant recombination between these sites is seen.
本报告展示了一项重组实验的结果，该实验旨在探究在 rosy 基因座区域内是否存在重组异源双链起始或终止的特殊位点。利用 DNA 限制性酶切位点多态性作为遗传标记，监测了两个物理上分离的 rosy 突变等位基因 ry301 和 ry2 之间的基因内重组事件。先前的研究表明，ry301 和 ry2 的基因转换频率均比单一位点突变低一个数量级。在先前的基因内定位研究中，这些突变与位于基因座内部位点的大的、明确界定的插入有关。在分子图谱上，它们分别代表 XDH 编码区第二和第三外显子中相距约 2.7 kb 的大插入。本研究监测了突变杂合基因型中的基因内重组，在该基因型中，DNA 同源性被这些大于基因座两侧 DNA 同源区域的大间断所破坏。如果起始/或终止需要在基因座两端有单独的位点，那么杂合子 rosy 基因座内的基因内重组应该会被消除。与预期相反，在这些位点之间观察到了显著的重组。
