群体遗传学课件

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,*,Chapter 11 Inheritance analysis of population and evolution,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 that 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,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,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 genetic 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 population,Mendelian population and gene pool,A population 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 generation,The genetic structure of population,Frequencies of all the 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,Calculating allele frequency,等位基因频率计算,The Hardy-Winberg Law,哈德-温伯格定律,1.The frequency of alleles does not change from generation to generation;in other words,the population does not evolve,2.After one generation of random mating,offspring genotype frequencies can be predicted from the 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,There is no selection,There is no mutation,There is no migration,The population is infinitely large,Individuals in the population mate randomly,没有选择,没有突变,没有迁移,群体无限大,群体中的个体随机交配,D=p,2,，H=2pq，R=q,2,The general case of allele and genotype frequencies,等位基因和基因型频率,the Hardy-weinberg law:calculating heterozygote frequency,基于,哈德-温伯格,计算杂合子频率,Extension of the Hardy-Weinberg law,哈德-温伯格定律的扩展,The equilibrium of multiple allele复等位基因的遗传平衡,基因型,I,A,I,A,I,A,i,I,B,I,B,I,B,i,I,A,I,B,ii,观察的表型频率,预计的表型频率,p,2,+2pr,q,2,+2qr,2pq,r,2,A,B,AB,O,The equilibrium of multiple allele,p+q+r=1,p=1-(q+r)=1-(q+r),1/2*2,(q+r),2,=q,2,+r,2,+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 Xap2+2pq+r2,Factors that alter allele frequencies in population,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，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,Fitness and selection coefficient,Fitness(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.Relatively,other genotypes range from 0 to 1,Selection coefficient(S):,The reduction of fitness results from the natural selection,S=1-W,For 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。,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=0,Natural election force,Mutation,突变,Forward and reverse-ward mutation,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，那么：,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,经过一个世代，基因频率的改变为：p=pu-qv,即子代群体：,P(A)=p-p,P(a)=q+p,当群体到达平衡时，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：,Migration,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。假设从另一群体(基因频率为pm,qm)迁入假设干个体，占新群体比例(迁入率)为m，那么：,迁入后新群体的基因频率为：,p1=(1-m)p0+mpm,q1=(1-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,In small populations,significant random fluctuations in allele frequencies are possible by chance deviation.The degree of,fluctuation increases as the population size decreases,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 deviation,in those samples composed 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 effe