时间：2023年6月28日（周三）14:00-15:30

Time：2:00-3:30 PM, Wednesday, June 28th, 2023

地点：西湖大学云谷校区学术环E10-222

Venue:  E10-222, Yungu Campus

主持人：西湖大学生命科学学院 特聘研究员 甄莹

Host: Dr. Ying Zhen, PI of School of Life Sciences

Jianzhi Zhang

Marshall W. Nirenberg Collegiate Professor of Ecology and Evolutionary Biology, 

University of Michigan

报告题目/Title: 

Revisiting the Neutral Theory of Molecular Evolution

讲座摘要/Abstract: 

The neutral theory asserts that most amino acid or nonsynonymous nucleotide substitutions in molecular evolution are selectively neutral and attributable to genetic drift.  The neutral theory has received substantial support, especially from comparative genomics in the last two decades, and is now widely accepted.  However, here we show that the key premise of the theory—beneficial mutations are extremely scarce—is violated.  Data from deep mutational scanning reveal that typically over 1% of nonsynonymous mutations are significantly beneficial, predicting a nonsynonymous substitution rate hundreds of times the neutral expectation and fraction of adaptive nonsynonymous substitutions exceeding 99%.  We propose that most observed beneficial mutations are nevertheless environment-specific because environment-independent beneficial mutations should have long been fixed.  Consequently, due to frequent environmental changes and mutational antagonistic pleiotropy across environments, the bulk of beneficial mutations seen at one time become deleterious soon after, so are rarely fixed.  Thus, despite the occurrence of adaptive tracking—continuous adaptation to a changing environment fueled by beneficial mutations, neutral substitutions prevail.  This quasi-neutral model of molecular evolution reconciles the relative prevalence of beneficial mutations with patterns of neutral evolution, is supported by population genetics simulation, empirical observations, and experimental evolution, and has implications for the fitness effects of genetic polymorphisms and the tempo and mode of molecular as well as phenotypic evolution.

讲座联系人/Contact:

科技合作部sci-tech02@westlake.edu.cn