Genetic drift is one of the four important factors affecting population genetic balance. Because its form of action is not as apparent as mutation, selection, and migration, which are intuitive and easy to understand, there are potential difficulties in understanding and mastering genetic drift. A particularly prominent problem is that the current introduction of genetic drift contents in textbooks is systematically insufficient. They are either even too rough, or completely neglecting the mathematical foundation such as the binomial theorem, resulting in long-term inadequate learning of genetic drift. In this paper, we summarize the five basic attributes of genetic drift, namely inherent, universal, random, non-directional, and regular features. Based on the concept that the genetic basis of genetic drift is the free combination of male and female gametes, we pointed out that the attribute of random sampling error is the inherent essential feature of genetic drift. Then step by step, from an extremely small population consisting of only one individual (N = 1), we deduced that the effect of genetic drift decreased while population size increased. Through introducing the mathematical model of the binomial theorem, the characteristics of the binomial distribution, and the results of computer simulations, the effect of genetic drift is visually and intuitively displayed to help the teaching the concept of genetic drift.
遗传漂变是影响群体遗传平衡的4个重要因素之一。因为它的作用形式不如突变、选择、迁移这3个因素那么直观易懂,所以在理解和掌握上存在较大的困难。尤其目前国内外教材中关于遗传漂变内容的介绍系统性不足,要么过于粗略,要么完全忽视了二项式定理这样的数学基础,造成了遗传漂变学习长期不到位的困难局面。本文总结得出遗传漂变的5个基本属性,即固有性、普遍性、随机性、无方向性、有规律性。进而从遗传漂变的遗传基础是雌雄配子的自由组合出发,指出抽样误差属性是遗传漂变固有的本质特征,并循序渐进地从N = 1这样仅仅由1个个体组成的极端小群体出发,推演出遗传漂变随着群体变大而影响减弱的性质,通过二项式定理数学模型、二项分布的特点、以及计算机模拟结果,形象直观地展示遗传漂变的作用,助力遗传漂变教学。.
Keywords: binomial distribution; binomial theorem; genetic drift; genetic equilibrium; population; sampling error.