Burton F H, Loeb D D, Edgell M H, Hutchison C A
Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
Mol Biol Evol. 1991 Sep;8(5):609-19. doi: 10.1093/oxfordjournals.molbev.a040671.
DNA sequence analysis of the same chromosomal region from two haplotypes of Mus musculus and from the related species M. caroli and M. pahari reveals the presence of long interspersed sequence one (LINES-1, or L1) elements residing at the same nucleotide position in the two most distantly related of the species (M. musculus and M. pahari). The DNA sequence of each of these L1 elements is more similar to that of other L1 elements from its own species than to the other. Thus, the L1 sequence at each of these sites is recent with respect to the divergence of the species. This could be a result of recent gene conversion of L1 elements inherited from a common ancestor or of two recent independent L1 insertion events at the same nucleotide position in the two species. Such specificity of insertion would be quite different from the apparent randomness of other characterized L1 insertion events, such as those in the beta-globin locus. If the recent L1 sequences arose at this site by gene conversion of an ancestral L1 element, then the absence of an L1 element at this location in the M. caroli chromosome examined could arise either from its precise deletion from M. caroli or from the segregation into M. caroli of a polymorphic chromosome present in the ancestral population which was missing this L1 element.
对小家鼠两个单倍型以及相关物种卡罗小家鼠和帕哈里小家鼠的同一染色体区域进行DNA序列分析，结果显示在两个亲缘关系最远的物种（小家鼠和帕哈里小家鼠）中，长散在序列1（LINE-1，或L1）元件位于相同的核苷酸位置。这些L1元件中每个元件的DNA序列与其自身物种的其他L1元件的序列相比，彼此之间更为相似。因此，就物种分化而言，这些位点处的L1序列是近期出现的。这可能是由于从共同祖先继承的L1元件发生了近期基因转换，或者是两个物种在相同核苷酸位置发生了两次近期独立的L1插入事件。这种插入的特异性与其他已表征的L1插入事件（如β-珠蛋白基因座中的那些事件）明显的随机性有很大不同。如果近期的L1序列是通过祖先L1元件的基因转换在该位点产生的，那么在所检测的卡罗小家鼠染色体的这个位置没有L1元件，可能是因为它从卡罗小家鼠中精确缺失，或者是由于祖先群体中存在的一条缺失该L1元件的多态性染色体分离到了卡罗小家鼠中。
