Mutation adaptation and genetic variation

所有活着的有机体都生活在不断发生突变的威胁下。突变出现的速度和它们的适合度效应是进化中最重要的两个量。大多数突变被认为是有害的，生命的许多常见特征可能至少部分是作为对有害突变的反应而进化的。这些特征包括二倍体、异交和有性繁殖和重组。尽管适应度降低的突变是常见的，但有些突变肯定是有益的，这些突变为适应性进化提供了原材料。这项拟议的研究调查了突变进化生物学的三个方面。首先，我们将探索植物中精子偏向突变传递的原因，这是我们实验室最近发现的一种现象。在哺乳动物和鸟类中已有男性偏向突变的记录，这主要是由于雄性生殖细胞系中的细胞分裂数量多于雌性生殖系所致。这种细胞分裂假说不应该适用于植物，因此在植物中的发现表明，其他因果过程肯定也在运行。这项研究的第二个主要目的是利用酿酒酵母研究突变率以及有性和重组的优势。突变率和适应度效应是进化生物学中两个最重要但尚未解决的问题。拟议研究的第三个主要部分调查了自交受精率不同的植物种群的遗传变异的维持。使用分子和数量遗传方法，我们将量化自交受精导致遗传变异变化的程度，从而可能导致高度自交受精的谱系在进化过程中明显缺乏持久性。

All living organisms exist under the constant threat of mutation. The rate at which mutations arise and their fitness effects are two of the most important quantities in evolution. The majority of mutations are believed to be deleterious, and many common features of life have probably evolved at least in part as a response to deleterious mutations. These features include diploidy, outcrossing and sexual reproduction and recombination. Despite the commonness of fitness-reducing mutations, some mutations must be beneficial, and these supply the raw material for adaptive evolution. The proposed research investigates three aspects of the evolutionary biology of mutations. In the first, we will explore the causes of sperm-biased mutation transmission in plants, a phenomenon recently discovered in our lab. Male-biased mutation had been documented in mammals and birds, where it was proposed to result largely from the greater number of cell divisions in the male than in the female germ line. This cell-division hypothesis should not apply to plants, so the discovery in plants shows that other causal processes must be operating. The second major thrust of the proposed research will study the mutation rate and the advantages of sex and recombination using the yeast Saccharomyces cerevisiae. The rate of mutation and the spectrum of fitness effects are two of the most important yet unresolved issues in evolutionary biology. The third major part of the proposed research investigates the maintenance of genetic variation in plant populations differing in rate of self-fertilization. Using both molecular and quantitative genetic measures, we will quantify the degree to which self-fertilization causes a change in genetic variation, and thus may contribute to the apparent lack of persistence of highly self-fertilizing lineages over evolutionary time.