CONSEQUENCES OF DELETERIOUS MUTATION

描述：迈克尔·林奇博士要求为一个为期5年的项目提供资金， 研究有害突变的性质和后果。 的 该项目由一个经验组成部分和一个理论 成分 实证研究提出，以确定性质和 水蚤和大肠杆菌的突变积累率。 有害突变影响的理论分析 灭绝率将通过计算机模拟进行。 将在线监测自发突变的累积 来源于水蚤的自然种群并作为克隆维持。 Inbred D. pulex和D.将通过诱导产生Pulicaria品系， 有性生殖和自花受精，经过15代， 从每个系产生四个克隆重复。 为了 允许突变的积累而不选择性消除，每个 将通过转移一个随机选择的 繁衍后代。 健康，定义为生存 在第10代时测定6窝的繁殖率 的间隔 适应度变化率和适应度方差 行之间将进行估计。 突变的性质和影响 将被表征。 需要分析的方面包括 环境敏感性、优势度、上位性和 有害影响。 从林奇博士的“四方程”中获得的估计 使用直接来自自然种群的克隆的方法将是 与从突变累积中获得的可比估计值相比， 实验 第二个实证研究将继续和扩大正在进行的突变- 积累实验使用E.杆菌 所有线路都将通过 通过单细胞瓶颈，每一代，与代表 每25个循环冷冻一次细胞。 各种生长特性 线相对于初始周期中的线的代表将 进行分析。 将估计的累积突变的方面 包括对生长参数、敏感性 环境条件和上位性。 实验将是 重复使用生长抑制和生长促进环境， 为了探索压力对产生率的影响， 突变的性质。 另一个扩展涉及监测菌株 携带已知的修复途径缺陷。 将进行数值模拟，以表征 有害突变对不同育种系统下灭绝率的影响 包括随机交配，专性无性，专性自我， 受精 允许突变效应根据 指定的分布，其中可能包括有益的， 有害突变 上位性的影响 （积极或消极的协同作用）的积累率将 被解决。 影响生育能力和生存能力的突变将 被研究。 种群变异对灭绝率的影响 大小和繁殖率由于环境因素以及 突变将被探索。

DESCRIPTION: Dr. Michael Lynch requests funds for a 5-year project to investigate the nature and consequences of deleterious mutations. The project is comprised of an empirical component and a theoretical component. Empirical studies are proposed to determine the nature and rate of accumulation of mutations in Daphnia and Escherichia coli. Theoretical analyses of the effects of deleterious mutations on extinction rates will be conducted through computer simulation. The accumulation of spontaneous mutations will be monitored in lines derived from natural populations of Daphnia and maintained as clones. Inbred D. pulex and D. pulicaria lines will be generated by inducing sexual reproduction and self-fertilization through 15 generations, and four clonal replicates will be generated from each line. In order to permit the accumulation of mutations without selective elimination, each culture will be maintained by transferring a single randomly chosen offspring to produce the next generation. Fitness, defined as survival and reproduction through six clutches, will be assayed at 10-generation intervals. The rate of change in fitness and the variance in fitness among lines will be estimated. The nature and effects of the mutations that accumulate will be characterized. Aspects to be analyzed include environmental sensitivity, dominance, epistasis, and magnitude of deleterious effects. Estimates obtained from Dr. Lynch's "four-equation" method using clones derived directly from natural populations will be compared to comparable estimates obtained from the mutation-accumulation experiments. A second empirical study will continue and expand on-going mutation- accumulation experiments using E. coli. All lines will be passed through a single-cell bottleneck each generation, with representative cells frozen every 25 cycles. Various growth characteristics of each line relative to representatives of the line in the initial cycle will be assayed. Aspects of the accumulated mutations that will be estimated include the distribution of effects on growth parameters, sensitivity to environmental conditions, and epistasis. The experiment will be repeated using growth-inhibiting and growth-enhancing environments in order to explore the effects of stress on the rate of generation and nature of mutations. Another extension involves monitoring strains carrying known deficiencies in repair pathways. Numerical simulations will be conducted to characterize the effects of deleterious mutations on extinction rates under various breeding systems including random mating, obligate asexuality, and obligate self- fertilization. Mutational effects will be allowed to vary according to a specified distribution, which may include beneficial as well as deleterious mutations. The effects of the nature of epistasis (positively or negatively synergistic) on the rate of accumulation will be addressed. Mutations affecting fertility as well as viability will be studied. The effects on extinction rates of variation in population size and reproductive rate due to environmental factors as well as mutations will be explored.