Garza J C, Freimer N B
Department of Integrative Biology, University of California, Berkeley 94720, USA.
Genome Res. 1996 Mar;6(3):211-7. doi: 10.1101/gr.6.3.211.
Homoplasy (convergence in the size of different alleles) at microsatellite loci was examined by sequencing multiple alleles of two compound microsatellites and single copies of alleles of the same size at two other compound loci in both chimpanzees and humans. At one of the two loci for which multiple alleles were sequenced, extensive homoplasy for size was uncovered both within and between species. At the three loci for which alleles of the same size were examined in the two species, sequencing demonstrated different internal structures. These results confirm theoretical predictions that a certain fraction of mutations at microsatellite loci should produce alleles that are identical in size but differ by a number of mutations. The sequence data reveal a previously unrecognized class of variation at microsatellites and open up the possibility that DNA sequencing may allow the extraction of more information from these loci, thus increasing their power as variable markers for genetic mapping studies. Conversely, the data also indicate that the assumption that alleles of the same size are identical in sequence, which is implicit in several methods of analysis, is violated in some cases. Therefore, caution should be used when employing microsatellites in phylogenetic and other studies in which the individuals being examined are separated by a great number of generations from a common ancestor.
通过对黑猩猩和人类的两个复合微卫星的多个等位基因以及另外两个复合位点上相同大小等位基因的单拷贝进行测序，研究了微卫星位点上的同塑性（不同等位基因大小的趋同）。在对多个等位基因进行测序的两个位点中的一个，在物种内部和物种之间都发现了广泛的大小同塑性。在两个物种中对相同大小等位基因进行检测的三个位点上，测序显示出不同的内部结构。这些结果证实了理论预测，即微卫星位点上一定比例的突变应该产生大小相同但突变数量不同的等位基因。序列数据揭示了微卫星上一类以前未被认识到的变异，并开启了DNA测序可能从这些位点提取更多信息的可能性，从而提高它们作为遗传图谱研究可变标记的能力。相反，数据也表明，在几种分析方法中隐含的相同大小等位基因在序列上相同的假设，在某些情况下是不成立的。因此，在系统发育和其他研究中使用微卫星时应谨慎，在这些研究中，被检测的个体与共同祖先相隔许多代。
