《群體遺傳學(xué)》PPT課件.ppt

1、Chapter 11 Inheritance analysis of population and evolution群體遺傳學(xué),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

2、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 群體遺傳學(xué) 一門(mén)研究群體的遺傳結(jié)構(gòu)及其變化規(guī)律的遺傳學(xué)分支學(xué)科，應(yīng)用數(shù)學(xué)和統(tǒng)計(jì)學(xué)的方法研究在群體中的基因頻率和基因型頻率以及影響這些頻率的選擇效應(yīng)和突變作用、遷移和遺傳漂變作用與遺傳結(jié)構(gòu)的關(guān)系，由此來(lái)探討進(jìn)化的機(jī)制,Pop

3、ulation and gene pools群體與基因庫(kù),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.

4、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 are

5、a, 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 群體與基因庫(kù) 一群能夠相互繁殖的個(gè)體，它們享有一

6、個(gè)共同的基因庫(kù) ，在有性繁殖生物中一個(gè)物種就是一個(gè)最大的孟德?tīng)柸后w 群體遺傳學(xué)中在一個(gè)世代所有個(gè)體共有的全部基因定義為一個(gè)基因庫(kù) 群體的遺傳結(jié)構(gòu)：指群體中各種基因的頻率和由不同的交配體所帶來(lái)的各種基因型頻率,Genotype frequency基因型頻率,Calculating allele frequency等位基因頻率計(jì)算,The Hardy-Winberg Law哈德-溫伯格定律,1. The frequency of alleles does not change from generation to generation; in other words, the population

7、 does not evolve 2. After one generation of random mating, offspring genotype frequencies can be predicted from the parent allele frequencies 一、等位基因頻率沒(méi)有改變，代代相傳。換句話(huà)說(shuō)，群體不進(jìn)化 二、 經(jīng)過(guò)一個(gè)世代的隨機(jī)交配，后代基因型頻率可以從親代等位基因頻率進(jìn)行預(yù)測(cè)，并保持平衡,A set of simple assumptions假設(shè)條件,There is no selection There is no mutation There is n

8、o migration The population is infinitely large Individuals in the population mate randomly 沒(méi)有選擇 沒(méi)有突變 沒(méi)有遷移 群體無(wú)限大 群體中的個(gè)體隨機(jī)交配,D=p2，H=2pq，R=q2,The general case of allele and genotype frequencies等位基因和基因型頻率,the Hardy-weinberg law: calculating heterozygote frequency基于哈德-溫伯格計(jì)算雜合子頻率,Extension of the Hardy-We

9、inberg law哈德-溫伯格定律的擴(kuò)展,The equilibrium of multiple allele復(fù)等位基因的遺傳平衡,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 = 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伴性基因的遺傳平衡,Male （XA Xa）(p q) Female （XA XA XA Xa Xa Xa）（p2+2p

10、q +r2）,Factors that alter allele frequencies in population改變?nèi)后w等位基因頻率的因素,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，群體是動(dòng)態(tài)的，其規(guī)模和基因庫(kù)的變化是常見(jiàn)的，符合在隨機(jī)交

11、配，選擇和突變，有同等生存能力和生育能力的情況下的假設(shè),Natural election自然選擇,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 reproducti

12、vity. 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 適合度與選擇系數(shù) 適合度，即適應(yīng)值，用W表示，是指在一定環(huán)境下，一個(gè)個(gè)體能夠生存并把他的基因傳遞給子代的相對(duì)能力。將具有最高生殖效能的基因

13、型的適應(yīng)值定為1，其它基因型在01之間。 選擇系數(shù)，用S表示，是指在一定環(huán)境下，某基因型在自然選擇作用下降低的適合度 S=1-W 致死或不育的基因型：S=1，W=0,Natural election force,Mutation突變,Forward and reverse-ward mutation正向和反向突變,在沒(méi)有其他因素影響時(shí)：設(shè)某一世代中，等位基因A, a的頻率分別為 P(A)=p, P(a)=q 正反突變率分別為u、v，則： u A=a v 在某一世代中： Aa的頻率為pu(正突變壓) aA的頻率為qv(反突變壓),Allele frequencies after mutation

14、 突變后的等位基因頻率,經(jīng)過(guò)一個(gè)世代，基因頻率的改變?yōu)椋簆=pu-qv 即子代群體： P(A)=p-p P(a)=q+p 當(dāng)群體達(dá)到平衡時(shí)，基因頻率保持不變，即： p=pu-qv=0(正反突變壓相等) 因此在平衡狀態(tài)下：,Migration遷移,Migration,遷移 指生物個(gè)體從一個(gè)居群進(jìn)入另一個(gè)居群 如果遷入個(gè)體的基因頻率與原群體不同，將改變基因頻率 在沒(méi)有其它因素影響下： 設(shè)一群體的基因頻率為p0, q0。若從另一群體(基因頻率為pm, qm)遷入若干個(gè)體，占新群體比例(遷入率)為m，則： 遷入后新群體的基因頻率為： p1=(1-m)p0+mpm q1=(1-m)q0+mqm 基因頻率

15、的改變?yōu)椋?p=p1-p0=(1-m)p0+mpm-p0=m(pm-p0) q=q1-q0=(1-m)q0+mqm-q0=m(qm-q0),各類(lèi)人群中FY-NULL*1等位基因的頻率,Genetic drift遺傳漂變,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 situatio

16、n known as genetic drift 在群體較小時(shí)，等位基因頻率會(huì)發(fā)生顯著的隨機(jī)波動(dòng)。隨著群體規(guī)模下降，波動(dòng)程度也增加的情況稱(chēng)為遺傳漂變,Population size and genetic drift群體大小與遺傳漂變,If the frequencies of the allele A and a in a population are p and q, respectively, the standard deviationin 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 effect: The effect that genotypes of a few induviduals control frequencies of their offspring Bottle nec