Cooper G, Rubinsztein D C, Amos W
University of Cambridge, Department of Zoology, Downing Street, Cambridge CB2 3EJ, UK.
Hum Mol Genet. 1998 Sep;7(9):1425-9. doi: 10.1093/hmg/7.9.1425.
A large majority of human microsatellite markers are longer than their homologues in chimpanzees, suggesting that more expansion mutations have occurred in the lineage leading to humans. However, such a length difference has also been explained as arising from the selection of unusually long microsatellites as genetic markers. In order to resolve this controversy and to establish the true source of the observed length differences, we have now conducted the necessary reciprocal study. We have compared the lengths of size-selected markers cloned from chimpanzees between this species and humans. We find that of 19 markers which were informative and polymorphic in both species, 13 are longer in humans. This result is incompatible with ascertainment bias being the sole explanation for the inter-specific length differences. We estimate that dinucleotide repeat microsatellites are an average of 3.2 repeat units longer in humans than in chimpanzees, implying a mutational bias in favour of microsatellite expansions and a higher average genome-wide microsatellite mutation rate in the human lineage.
绝大多数人类微卫星标记比黑猩猩中的同源标记长，这表明在人类谱系中发生了更多的扩增突变。然而，这种长度差异也被解释为是由于选择了异常长的微卫星作为遗传标记所致。为了解决这一争议并确定观察到的长度差异的真正来源，我们现在进行了必要的反向研究。我们比较了从黑猩猩和人类中克隆的大小选择标记的长度。我们发现，在两个物种中均具有信息性和多态性的19个标记中，有13个在人类中更长。这一结果与确定偏倚是种间长度差异的唯一解释不相符。我们估计，二核苷酸重复微卫星在人类中平均比在黑猩猩中长3.2个重复单元，这意味着存在有利于微卫星扩增的突变偏倚以及人类谱系中全基因组范围内微卫星平均突变率更高。
