1、Chapter 11 Inheritance analysis of population and evolution群体遗传学群体遗传学 Population genetics A branch discipline of genetics to investigate the genetic structure and variation of popualtions;that is,the discipline within genetics studies that changes in gene and genotype frequencies,and the factors tha
2、t alter the frequencies such as selection,mutation,migration,as well as random genetic drift by the mathematical and statistical method,thus to explore the mechanism of biology evolution 群体遗传学群体遗传学 一门研究群体的遗传结构及其变化规律的遗传学分支学科，应用一门研究群体的遗传结构及其变化规律的遗传学分支学科，应用数学和统计学的方法研究在群体中的基因频率和基因型频率以及数学和统计学的方法研究在群体中的基因
3、频率和基因型频率以及影响这些频率的选择效应和突变作用、迁移和遗传漂变作用与遗影响这些频率的选择效应和突变作用、迁移和遗传漂变作用与遗传结构的关系，由此来探讨进化的机制传结构的关系，由此来探讨进化的机制Population and gene pools群体与基因库Individuals can carry only two different alleles of a given gene.A group of individuals can carry a larger number of different alleles,giving rise to a reservoir of gene
4、tic diversity.The diversity contained in the population can be measured by the Hardy-Weinberg Law.Mutation is the ultimate source of genetic variation,and other factor such as drift,migration,and selection can alter the amount of genetic variation in populationMendelian population and gene poolA pop
5、ulation is a group of individuals from the same species that lives in the same geographic area,and that actually or potentially interbreeds.A gene pool consists of all gametes made by all the breeding members of a population in single generationThe genetic structure of populationFrequencies of all t
6、he genes and various genotypes consisted of them in a population群体与基因库 一群能够相互繁殖的个体，它们享有一个共同的基因库，在有性繁殖生物中一个物种就是一个最大的孟德尔群体群体遗传学中在一个世代所有个体共有的全部基因定义为一个基因库群体的遗传结构：指群体中各种基因的频率和由不同的交配体所带来的各种基因型频率Genotype frequency基因型频率基因型频率 基因型个体数基因型频率AADD=D/NAaHH=H/NaaRR=R/NN1Calculating allele frequency等位基因频率计算等位基因频率计算等位
7、基因基因座数基因频率A2D+Hp=(2D+H)/2ND+Ha2R+Hq=(2R+H)/2NR+H2N11The Hardy-Winberg Law哈德哈德-温伯格定律温伯格定律1.The frequency of alleles does not change from generation to generation;in other words,the population does not evolve2.After one generation of random mating,offspring genotype frequencies can be predicted from t
8、he parent allele frequencies一、等位基因频率没有改变，代代相传。换句话说，群体不进化 二、经过一个世代的随机交配，后代基因型频率可以从亲代等位基因频率进行预测，并保持平衡A set of simple assumptions假设条件假设条件There is no selectionThere is no mutationThere is no migration The population is infinitely large Individuals in the population mate randomly没有选择没有选择 没有突变没有突变 没有迁移没有迁
9、移 群体无限大群体无限大 群体中的个体随机交配群体中的个体随机交配The general case of allele and genotype frequencies等位基因和基因型频率等位基因和基因型频率the Hardy-weinberg law:calculating heterozygote frequency基于基于哈德哈德-温伯格温伯格计算杂合子频率计算杂合子频率 Extension of the Hardy-Weinberg law哈德哈德-温伯格定律的扩展温伯格定律的扩展 The equilibrium of multiple allele复等位基因的遗传平衡复等位基因的遗传
10、平衡基因型IA IA IAiIB IB IBiIA IBii观 察 的 表型频率预 计 的 表型频率 p2+2prq2+2qr 2pqr2ABABOThe equilibrium of multiple allele p+q+r=1 p=1-(q+r)=1-(q+r)1/2*2 (q+r)2=q2+r2+2qr=B+O p=1-(B+O)*1/2 q=1-(A+O)*1/2 r=1-(p+q)The equilibrium of sex-linked gene伴性基因的遗传平衡Male （XA Xa）(p q)Female（XA XA XA Xa Xa Xa）（p2+2pq+r2）Factor
11、s that alter allele frequencies in population改变群体等位基因频率的因素改变群体等位基因频率的因素In nature,population are dynamic,and change in size and gene pool are common,which meet the assumptions of random mating,absence of selection and mutation,and equal viability and fertility在自然界中，群体是动态的，其规模和基因库的变化是常见的，符合在随机交配，选择和突变
12、，有同等生存能力和生育能力的情况下的假设Natural election自然选择自然选择Fitness and selection coefficientFitness(W),adaptive value,it is the capacity for an individual to survive to pass its genes to the offspring under a certain condition.The adaptive value is defined as 1 for the genotype with the highest reproductivity.Rela
13、tively,other genotypes range from 0 to 1Selection coefficient(S):The reduction of fitness results from the natural selectionS=1-WFor lethal or sterile genotypes,their S and W are defined as 1 and 0,respectively 适合度与选择系数 适合度，即适应值，用W表示，是指在一定环境下，一个个体能够生存并把他的基因传递给子代的相对能力。将具有最高生殖效能的基因型的适应值定为1，其它基因型在01之间。
14、选择系数，用S表示，是指在一定环境下，某基因型在自然选择作用下降低的适合度S=1-W 致死或不育的基因型：S=1，W=0Natural election forceMutation突变突变Forward and reverse-ward mutation正向和反向突变正向和反向突变 在没有其他因素影响时：设某一世代中，等位基因A,a的频率分别为 P(A)=p,P(a)=q 正反突变率分别为u、v，则：u A=a v 在某一世代中：Aa的频率为pu(正突变压)aA的频率为qv(反突变压)Allele frequencies after mutation 突变后的等位基因频率突变后的等位基因频率经
15、过一个世代，基因频率的改变为：p=pu-qv即子代群体：P(A)=p-p P(a)=q+p当群体达到平衡时，基因频率保持不变，即：p=pu-qv=0(正反突变压相等)因此在平衡状态下：vuuqvuvp-p)v(qvpupqqpqv pup=pu-qv1110Migration迁移迁移Migration 迁移 指生物个体从一个居群进入另一个居群 如果迁入个体的基因频率与原群体不同，将改变基因频率 在没有其它因素影响下：设一群体的基因频率为p0,q0。若从另一群体(基因频率为pm,qm)迁入若干个体，占新群体比例(迁入率)为m，则：迁入后新群体的基因频率为：p1=(1-m)p0+mpm q1=(1
16、-m)q0+mqm 基因频率的改变为：p=p1-p0=(1-m)p0+mpm-p0=m(pm-p0)q=q1-q0=(1-m)q0+mqm-q0=m(qm-q0)各类人群中FY-NULL*1等位基因的频率Genetic drift遗传漂变遗传漂变In small populations,significant random fluctuations in allele frequencies are possible by chance deviation.The degree of fluctuation increases as the population size decreases,
17、a situation known as genetic drift在群体较小时，等位基因频率会发生显著的随机波动。随着群体规模下降，波动程度也在群体较小时，等位基因频率会发生显著的随机波动。随着群体规模下降，波动程度也增加的情况称为遗传漂变增加的情况称为遗传漂变Population size and genetic drift群体大小与遗传漂变 If the frequencies of the allele A and a in a population are p and q,respectively,the standard deviationin those samples comp
18、osed of N induviduals is expressed as:=(pq/2N)1/2,which indicates that the more the sampling err are the less those samples are Founder effect:The effect that genotypes of a few induviduals control frequencies of their offspring Bottle neck effect:Changes in allelic frequencies accidentally happen in the few induviduals subjective to extinction群体大小与抽样误差的关系奠基者效应：奠基者效应：由少数个体的基因频率决定了他们后代中的基因频率的效应瓶颈效应：群体中个体数目急剧减少甚至灭绝的等位基因频率发生的偶然变异Non-random mating非随机交配非随机交配Calculating the coefficient of inbreeding近交系数的计算近交系数的计算
