Reed K M, Beukeboom L W, Eickbush D G, Werren J H
Department of Biology, University of Rochester, NY 14627.
J Mol Evol. 1994 Apr;38(4):352-62. doi: 10.1007/BF00163152.
The Paternal-Sex-Ratio (PSR) chromosome of Nasonia vitripennis contains several families of repetitive DNAs that show significant sequence divergence but share two palindromic regions. This study reports on the analysis of junctions between two of these repetitive DNA families (psr2 and psr18). Three lambda clones that hybridized to both repeat families were isolated from PSR-genomic DNA libraries through multiple screenings and analyzed by Southern blots. Analysis of clones showed a region in which the two repeat types are interspersed, flanked by uniform blocks of each repeat type. PCR amplification of genomic DNA confirmed the contiguous arrangement of psr2 and psr18 on PSR and identified an additional junction region between these repeats that was not present in the lambda inserts. We isolated and sequenced 41 clones from the lambda inserts and genomic PCR products containing junction sequences. Sequence analysis showed that all transitions between psr2 and psr18 repeats occurred near one of the two palindromes. Based on the inheritance pattern of PSR, recombination between repeats on this chromosome must be mitotic (rather than meiotic) in origin. The occurrence of exchanges near the palindromes suggests that these sequences enhance recombination between repeat units. Rapid amplification of repetitive DNA may have been an important factor in the evolution of the PSR chromosome.
丽蝇蛹集金小蜂的父本性别比（PSR）染色体包含几个重复DNA家族，这些家族显示出显著的序列差异，但共享两个回文区域。本研究报告了对其中两个重复DNA家族（psr2和psr18）之间连接点的分析。通过多次筛选从PSR基因组DNA文库中分离出三个与两个重复家族都杂交的λ克隆，并通过Southern杂交进行分析。对克隆的分析显示了一个区域，其中两种重复类型相互穿插，两侧是每种重复类型的均匀片段。基因组DNA的PCR扩增证实了psr2和psr18在PSR上的连续排列，并确定了这些重复序列之间一个λ插入片段中不存在的额外连接区域。我们从λ插入片段和含有连接序列的基因组PCR产物中分离并测序了41个克隆。序列分析表明，psr2和psr18重复序列之间的所有转换都发生在两个回文之一附近。基于PSR的遗传模式，这条染色体上重复序列之间的重组一定起源于有丝分裂（而非减数分裂）。回文附近发生交换表明这些序列增强了重复单元之间的重组。重复DNA的快速扩增可能是PSR染色体进化中的一个重要因素。
