Wang Xiaoxia, Thomas Stephanie D, Zhang Jianzhi
Department of Ecology and Evolutionary Biology, University of Michigan, 830 North University Avenue, Ann Arbor, MI 48109, USA.
Hum Mol Genet. 2004 Nov 1;13(21):2671-8. doi: 10.1093/hmg/ddh289. Epub 2004 Sep 14.
Bitter taste perception prevents mammals from ingesting poisonous substances because many toxins taste bitter and cause aversion. We hypothesize that human bitter taste receptor (TAS2R) genes might be relaxed from selective constraints because of the change in diet, use of fire and reliance on other means of toxin avoidance that emerged in human evolution. Here, we examine the intra-specific variations of all 25 genes of the human TAS2R repertoire. Our data show hallmarks of neutral evolution, including similar rates of synonymous (d(S)) and non-synonymous (d(N)) nucleotide changes among rare polymorphisms, common polymorphisms and substitutions; no variation in d(N)/d(S) among functional domains; segregation of pseudogene alleles within species and fixation of loss-of-function mutations. These results, together with previous findings of large numbers of loss-of-function mutations in olfactory, pheromonal and visual sensory genes in humans, suggest surprisingly reduced sensory capabilities of humans in comparison with many other mammals.
苦味感知能防止哺乳动物摄入有毒物质，因为许多毒素尝起来是苦的，并会引起反感。我们推测，由于人类进化过程中饮食的变化、火的使用以及对其他避免毒素方法的依赖，人类苦味受体（TAS2R）基因可能不再受到选择性限制。在此，我们研究了人类TAS2R基因库中所有25个基因的种内变异。我们的数据显示出中性进化的特征，包括稀有多态性、常见多态性和替换中同义（d(S)）和非同义（d(N)）核苷酸变化的相似速率；功能域之间d(N)/d(S)无变化；物种内假基因等位基因的分离以及功能丧失突变的固定。这些结果，连同之前关于人类嗅觉、信息素和视觉感觉基因中大量功能丧失突变的发现，表明与许多其他哺乳动物相比，人类的感觉能力惊人地降低。
