tailieunhanh - ECOTOXICOLOGY: A Comprehensive Treatment - Chapter 17

Di truyền học Dân số: Thiệt hại và Stochastic Động thái của dòng mầm Bởi vì họ cung cấp không phải là lợi thế cũng không trách nhiệm, các đột biến trung tính hoặc bị mất đi hay cố định bởi những thay đổi ngẫu nhiên trong tần số alen từ thế hệ này sang thế hệ khác. Do đó, động lực tiến hóa của các đột biến trung tính đầy đủ mô tả bởi phương trình sử dụng lao động quy mô dân số, N, quy mô dân số hiệu quả, Ne, tỷ lệ đột biến trung tính, u, và tỷ. | 17 Population Genetics Damage and Stochastic Dynamics of the Germ Line Because they offer neither advantage nor liability neutral mutations are either lost or fixed by stochastic changes in allele frequency from generation to generation. Thus the evolutionary dynamics of neutral mutations are adequately described by equations employing population size N effective population size Ne neutral mutation rate u and migration rate m. Neutral theory has had a tremendous impact on population genetics and many empirical patterns are consistent with predictions arising from neutral theory. Mitton 1997 OVERVIEW This chapter describes key processes in population genetics other than adaptation and natural selection. Initial discussion outlines briefly how toxicants can damage DNA and then stochastic dynamics of population genetics are described. Understanding toxicant effects on stochastic processes is as important as understanding toxicant-driven natural selection. Qualities of toxicant-exposed populations can be directly influenced by stochastic or neutral processes. Neutral is used here only to indicate genetic processes or phenomena not involving natural selection. Ecotoxicologists often focus on adaptation via natural selection and pay less attention than warranted to neutral processes. At best neutral processes are invoked as null hypotheses during testing for selection. Current applications of such hypothesis tests by ecotoxicologists are prone to neglect experimentwise Type I errors that is prone to inappropriately favor the statistical detection of selection and to reject the neutral theory-based null hypothesis. In the lead chapter of Genetics and Ecotoxicology Forbes 1999 Forbes states The ten contributions to this volume address a number of key issues that taken together summarize our current understanding of the relationship between genetics and ecotoxicology. Despite the clear value of Forbes s book this statement is dismaying. Aside from one chapter .