群体的遗传平衡

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 Population Genetics,第十一章 群体的遗传平衡,11.1 Concept,11.1.1 Gene frequency,11.1.2 Genotype frequency,11.2 Hardy-Weinberg law 哈迪温伯格平衡,11.2.1 Equilibrium in gene frequencies,基因频率的恒定,11.2.2 Equilibrium in genotype frequencies,基因型频率的恒定,11.3 Calculating multi-allele frequencies,复等位基因频率的计算,11.4 Genotype frequencies in the self-crossing population,自交群体中基因型频率的变化,11.5 Transfer of recessive lethal gene in the random,mating population 互交群体中隐性致死基因的传递,Genes in populations:hardy-weinberg equilibrium,群体中的基因:哈迪 温伯格平衡,Population genetics 群体遗传学,Deme 同类群,Frequency 频率,Gene pool 基因库,Randomly 随机地,Random mating 随机交配,Selection 选择,Migration 迁移,11.1 Concept,Population genetics is the study of alleles of genes in populations,and the force which maintain or change the frequencies of particular alleles and genotypes in populations.,The total genetic stock of the population is its gene pool.Individuals have a selection of alleles from that gene pool,possibly taken randomly.,群体：随机交配,(,异交,),，产生可育后代的动态个体群,dynamic,孟德尔氏群体：基因遗传表现符合孟德尔遗传规律的,群体。,群体遗传组成变化 物种进化。,研究群体遗传学 阐明物种进化机制,群体基因库,-,群体中遗传物质总和,群体遗传学,研究群体中维持或改变特定等位基因及 基因型频率的作用力的学科。,研究基因在群体中的传递情况和基因频率、基因型频率变化的科学。,研究群体遗传结构及其变化规律的遗传学分支学科。,Gene/allele frequencies,基因频率,某群体中某一等位基因数与位点上出现的基因总数之比（该位点上可能出现的所有基因类型的频率之 和等于,1,，,p+q=1,）,14.1.2 Genotype frequencies,基因型频率,同一基因座上某种基因型个体数与总群体数之比（群体中某基因座上所有基因型频率之和等于,1,，,P+H+Q=1,）,Eg.,100个体 AA 30，Aa 60，aa 10,基因型频率为：AA Aa aa,30%60%10%,设:P H Q (P+H+Q,=100%）,基因数：A 60 60 0 =120,a 0 60 20 =80,总基因数=60+60+60+20=200,基因频率：p(A)=120/200 100%=60%,q(a)=80/200100%=40%(p+q=100%),即：p,(A),=(2P+H)/(2P+H+H+2Q)=(2P+H)/2(P+H+Q)=P+1/2 H,q,(a),=(H+2Q)/(2P+H+H+2Q)=(2Q+H)/2(P+H+Q)=Q+1/2H,即：,p+q=P+1/2H+Q+1/2H=P+H+Q=1,11.2 Hardy-Weinberg law(哈迪温伯格平衡定律),Hardy and Weinberg independently developed this calculation to show that an equilibrium in genotype frequencies will occur after one generation of random mating,and those genotype can be calculated from allele frequencies.The equilibrium frequencies will be maintained from generation to generation unless some force changes the allele frequencies,1908年，英国数学家Hardy、德国内科医生Weinberg分别得出该定律,Hardy和Weinberg各自独立提出此平衡式:,经过一个世代的随机交配，群体中基因型频率恒定，其频率可由等位基因频率推算。这种衡定代代保持，除非某种因素改变等位基因的频率。,在一个,无限大,的,随机交配,的群体中，基因频率和基因型频率在没有,迁移、突变、自然选择,的条件下，世代相传不发生变化。,大群体,Large population,无限大 无遗传漂变,无迁移,No immigration,不发生迁入迁出,随机交配,Random mating,有性交配（泛交）机会均等且随机,基因频率和基因型频率恒定的五大条件：,无突变,No mutation,无频发和非频发突变,无选择,No selection,无自然选择作用,Populations that satisfy all five assumptions above are said to be at Hardy-Weinberg equilibrium.,11.2.1 Equilibrium in gene frequencies,基因频率的恒定,Allele frequencies is found by adding up the number of copies of each allele in a population and expressing it as a frequency.,A population of diploid individuals has 2N alleles.Each Aa heterozygote has one A allele and one a allele,each AA homozygote has two A alleles,each aa has two a alleles.,基因频率的恒定：,假设亲本交配产生精、卵配子，各,配子中基因频率p,(A),和q,(a),；,配子随机组合形成合子，其基因型：,父本,母本,p(A),q(a),p(A),p,2,AA,pqAa,q(a),pqAa,q,2,aa,基因型之比：,p,2,AA :2pqAa :q,2,aa=p,2,:2pq:q,2,=1:2:1,子一代配子基因频率：,A=(2p,2,+2pq)/(2p,2,+2pq+2pq+2q,2,)=p,2,+pq=p(p+q)=p,或=P+1/2H=p,2,+1/22pq=p(p+q)=p,a=(2q,2,+2pq)/(2p,2,+2pq+2pq+2q,2,)=q,2,+pq=q(p+q)=q,或 Q+1/2H=q,2,+1/22pq=q(p+q)=q,F1 基因A频率=p；基因a频率=q；,且世代相传-,基因频率的恒定,e.g.亲本配子中p=0.7,q=0.3，,求子代形成配子的基因频率？,lets see the answer,合子基因型,：,父本,母本,p(A)=,0.7,q(a)=,0.3,p(A)=0.7,p,2,(AA)=0.49,pq(Aa)=0.21,q(a)=0.3,pq(Aa)=0.21,q,2,(aa)=0.09,子代形成配子的基因频率：,A=,(2p,2,+2pq)/(2p,2,+2pq+2pq+2q,2,),=p,2,+pq=0.49+0.21=,0.70,a=(2q,2,+2pq)/(2p,2,+2pq+2pq+2q,2,),=q,2,+pq=0.09+0.21=,0.30,A、a频率仍分别为0.7和0.3,群体该基因座上 基因频率总和=0.7+0.3=1,基因型频率总和=0.49+20.21+0.09=1,p,2,(AA)+2pq(Aa)+q,2,(aa)=,p,(A),+q,(a),2,=P+H+Q=1,11.2.2 Equilibrium in genotype frequencies,基因型频率的恒定,Equilibrium in genotype frequencies will be reached in zygotes after one round of random mating.,The total expected genotype frequencies are predicted by the Hardy-Weinberg equation:,p,2,(AA)+2pq(Aa)+q,2,(aa),If there are two alleles,A,and,a,with frequencies p and q respectively,then the expected frequency of,AA,homozygotes is p,2,of,Aa,heterozygotes is 2pq,and of,aa,homozygotes is q,2,.,三种基因型个体间随机交配，产生的不同基因型频率为：,P,(AA),H,(Aa),Q,(aa),P,(AA),P,2,P,H,P,Q,H,(Aa),P,H,H,2,H,Q,Q,(aa),P,Q,H,Q,Q,2,父本基因型及频率,母本基因型及频率,AAAA,P,2,=,P,2,AAAa,2PH =,PH,PH,AAaa,2PQ =,2PQ,AaAa,H,2,=,1/4H,2,2/4H,2,1/4H,2,Aaaa,2HQ =,HQ,HQ,aaaa,Q,2,=,Q,2,AA Aa aa,全部后代的基因型频率为：,P,2,+2PH+2PQ+H,2,+2HQ+Q,2,=P,2,+PH+1/4H,2,+PH+2PQ+1/2H,2,+HQ+1/4H,2,+HQ+Q,2,=(P+1/2H),2,+2(1/2PH+PQ+1/4H,2,+1/2HQ)+(Q+1/2H),2,=(P+1/2H),2,+2P(1/2H+Q)+1/2H(1/2H+Q)+(Q+1/2H),2,=(P+1/2H),2,+2(Q+1/2H)(P+1/2H)+(Q+1/2H),2,AA Aa,aa,=p,2,+2pq +q,2,=1,后代基因型频率与亲本一致,相同基因位点上的基因型频率总和为1,e.g.苯丙酮尿症隐性遗传病患者在美国的发病率为 1/10000，问美国人群中，该隐性基因频率和携带该隐性基因的杂合子基因型频率是多少？,The frequency of homozygous recessiveness is q,2,so the frequency of the recessive allele is q,and the frequency of the dominant allele p=(1-q),解：设该隐性基因为a，杂合子基因型为Aa，发病率即纯合隐性aa基因型频率为：1/10000 aa=q,2,=1/10000 q=1/10000=0.01 p+q=1 p=1-0.01=0.99 Aa=2pq Aa=20.990.01=0.0198 答:q=1%Aa=1.9