"AB"“BB""AA"Totalgenotype442012number of individuals"A""B"alleleTotal281240numberofchromosomes0.31.00.7allelefrequencyAllelefrequency:A: (12×2 + 4)/(20×2)= 0.7B: (4 + 4x2)/(20x2) = 0.3Fig.20.221-11
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 21-11 Allele frequency: A: (122 + 4)/(202) = 0.7 B: (4 + 42)/(202) = 0.3 Fig. 20.2
Calculating allele frequencies from genotype frequenciesGenotypes in firstRrRRrrgenerationNumberof individualsNRRNrrNRrinfirstgenerationAlleletypes infirst generation2NRR + NRrp=frequencyof RAllelefrequenciesin2Ntotalfirst generationgametesNRr + 2Nrrq=frequencyof r=2NtotalgametesNtotal=NRR+NRr+Nrr2Ntotal=totalchromosomes21-12
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 21-12 Calculating allele frequencies from genotype frequencies
The Hardy-Weinberg law correlates allele andgenotypefrequenciesA model for understanding allele,genotype, and phenotypefrequencies for single gene traits in a genetically stablepopulation.Developed independently in 1908 byGodfreyH.HardyWilhelmWeinberg21-13
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 21-13 The Hardy The Hardy-Weinberg law correlates allele and Weinberg law correlates allele and genotype frequencies genotype frequencies A model for understanding alle A model for understanding allele, genotype, and phenotype le, genotype, and phenotype frequencies for single gene traits in a genetically stable frequencies for single gene traits in a genetically stable population. population. Developed independently in 1908 by Developed independently in 1908 by Godfrey H. Hardy Wilhelm Weinberg
Fivekeyassumptions of population1.Populations large enough to minimize randomized events.2.Individuals mate at random3.No new mutations appear in gene pool.4No migration in or out of population5.All genotypes have equal chances of survival and reproductionIf all assumptions hold, population is in Hardy-Weinbergequilibrium.Allele frequencies do not change.Genotype frequencies can be predicted21-14
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 21-14 Five key assumptions of population Five key assumptions of population 1. Populations large enough to minimize randomized events. Populations large enough to minimize randomized events. 2. Individuals mate at random. Individuals mate at random. 3. No new mutations appear in gene pool. No new mutations appear in gene pool. 4. No migration in or out of population No migration in or out of population 5. All genotypes have equal chances of survival and reproduction. All genotypes have equal chances of survival and reproduction. If all assumptions hold, population is in If all assumptions hold, population is in Hardy-Weinberg Weinberg equilibrium equilibrium. Allele frequencies do not change. Allele frequencies do not change. Genotype frequencies can be predicted. Genotype frequencies can be predicted
Using gamete allele frequencies to calculate genotypefrequencies in the next generationSpermRAllelerFrequencyqpRRRrAlleleRp2FrequencypqS63RrAllelerrq2FrequencypqC21-15
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 21-15 Using gamete allele frequencies to calculate genotype Using gamete allele frequencies to calculate genotype frequencies in the next generation frequencies in the next generation