Hughes A L
Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.
Heredity (Edinb). 2007 Oct;99(4):364-73. doi: 10.1038/sj.hdy.6801031. Epub 2007 Jul 11.
Recent years have seen an explosion of interest in evidence for positive Darwinian selection at the molecular level. This quest has been hampered by the use of statistical methods that fail adequately to rule out alternative hypotheses, particularly the relaxation of purifying selection and the effects of population bottlenecks, during which the effectiveness of purifying selection is reduced. A further problem has been the assumption that positive selection will generally involve repeated amino-acid changes to a single protein. This model was derived from the case of the vertebrate major histocompatibility complex (MHC), but the MHC proteins are unusual in being involved in protein-protein recognition and in a co-evolutionary process of pathogens. There is no reason to suppose that repeated amino-acid changes to a single protein are involved in selectively advantageous phenotypes in general. Rather adaptive phenotypes are much more likely to result from other causes, including single amino-acid changes; deletion or silencing of genes or changes in the pattern of gene expression.
近年来，人们对分子水平上正向达尔文选择的证据兴趣激增。由于使用的统计方法未能充分排除其他假设，尤其是净化选择的放松和种群瓶颈的影响（在此期间净化选择的有效性降低），这一探索受到了阻碍。另一个问题是假设正向选择通常会涉及单个蛋白质的重复氨基酸变化。这个模型源自脊椎动物主要组织相容性复合体（MHC）的案例，但MHC蛋白不同寻常之处在于它参与蛋白质-蛋白质识别以及病原体的共同进化过程。一般而言，没有理由认为单个蛋白质的重复氨基酸变化会涉及选择性优势表型。相反，适应性表型更有可能由其他原因导致，包括单个氨基酸变化；基因的缺失或沉默或基因表达模式的改变。
