Mutation adaptation and genetic variation

所有的生物体都在不断的突变威胁下生存。突变发生的速率和它们的适应性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，生命的许多共同特征可能至少部分地进化为对有害突变的反应。这些特征包括二倍体、异交、有性生殖和重组。尽管降低适应性的突变很常见，但有些突变肯定是有益的，而这些突变为适应性进化提供了原材料。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播的原因，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经记录了偏向雄性的突变，据推测，这主要是由于雄性生殖细胞的细胞分裂次数多于雌性生殖细胞。这种细胞分裂假说不应该适用于植物，所以在植物中的发现表明，其他因果过程必须运作。拟议研究的第二个主要重点将研究突变率和性别的优势和重组使用的酵母酿酒酵母。突变率和适应度效应谱是进化生物学中两个最重要但尚未解决的问题。本研究的第三个主要部分是研究在不同的自花受精率的植物种群中遗传变异的维持。使用分子和定量遗传措施，我们将量化的程度，自花受精导致遗传变异的变化，从而可能有助于明显缺乏持久性的高度自我繁殖的血统在进化过程中。

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.