《Nature》：自然突变的速度
了解真核动物自然突变的速度非常重要，因为它与从演化到遗传疾病等生物学的许多领域都有关系。由于自然选择的影响，估计突变速度的很多方法效果都不是很好，但在用线虫（Caenorhabditis elegans）的一组突变积累品系所做的一个新的实验中，这个问题已经避免。通过让实验室培养出的一个品系的数百代个体通过一个严重的种群瓶颈，每一代只有一个线虫，这样就绕过了自然选择，避免了兄弟姐妹之间的竞争。这一体系中的突变速度是以前间接估计结果的10倍。
High mutation rate and predominance of insertions in the Caenorhabditis elegans nuclear genome
Mutations have pivotal functions in the onset of genetic diseases and are the fundamental substrate for evolution. However, present estimates of the spontaneous mutation rate and spectrum are derived from indirect and biased measurements. For instance, mutation rate estimates for Caenorhabditis elegans are extrapolated from observations on a few genetic loci with visible phenotypes and vary over an order of magnitude. Alternative approaches in mammals, relying on phylogenetic comparisons of pseudogene loci and fourfold degenerate codon positions, suffer from uncertainties in the actual number of generations separating the compared species and the inability to exclude biases associated with natural selection. Here we provide a direct and unbiased estimate of the nuclear mutation rate and its molecular spectrum with a set of C. elegans mutation-accumulation lines that reveal a mutation rate about tenfold higher than previous indirect estimates and an excess of insertions over deletions. Because deletions dominate patterns of C. elegans pseudogene variation, our observations indicate that natural selection might be significant in promoting small genome size, and challenge the prevalent assumption that pseudogene divergence accurately reflects the spontaneous mutation spectrum.
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