《医学遗传学》课程PPT教学课件（留学生 Medical Genetics）07 Chapter Population Genetics

MedicalGenetics Population Genetics

Population Genetics Medical Genetics

Emphasis Gene Frequency Genotypic Frequency *Law of Genetic Equilibrium Factors that Alter Genetic Equilibrium —Mutation,Selection Consanguineous Marriage Genetic Load

Emphasis ❖ Gene Frequency & Genotypic Frequency ❖ Law of Genetic Equilibrium ❖ Factors that Alter Genetic Equilibrium —— Mutation, Selection ❖ Consanguineous Marriage ❖ Genetic Load

Population genetics investigates genetic structure and genetic variation among individuals within groups. Mendelian population is a group of interbreeding individuals,who live in the same place and share a common set of genes (gene pool)

Population genetics investigates genetic structure and genetic variation among individuals within groups. Mendelian population is a group of interbreeding individuals, who live in the same place and share a common set of genes (gene pool)

Gene Frequency Genotypic Frequency Allelic frequency:a proportion or a percent of allele. Genotypic frequency:the number of individuals with one particular genotype divided by the total number of individuals in the population

Allelic frequency: a proportion or a percent of allele. Genotypic frequency: the number of individuals with one particular genotype divided by the total number of individuals in the population. Gene Frequency & Genotypic Frequency

Gene Frequency Genotypic Frequency M Genotype:MM 5;MN 7;NN 4 Allelic frequency of M:p三(2×5+7)/2×16)=0.5312 Allelic frequency of N:q=(2X4+7)/(2X16)=0.4688

Gene Frequency & Genotypic Frequency M N Genotype: MM 5; MN 7; NN 4 Allelic frequency of M：p ＝(2×5＋7)/(2×16)＝0.5312 Allelic frequency of N：q ＝(2×4＋7)/(2×16)＝0.4688

Law of Genetic Equilibrium Hardy-Weinberg law Hardy GH Weinberg W

Law of Genetic Equilibrium Hardy-Weinberg law Hardy GH Weinberg W

Law of Genetic Equilibrium Hardy-Weinberg law Explains how Mendelian segregation influences allelic and genotypic frequencies in a population

Explains how Mendelian segregation influences allelic and genotypic frequencies in a population. Law of Genetic Equilibrium Hardy-Weinberg law

Law of Genetic Equilibrium Hardy-Weinberg law Assumptions *Large population Random mating No natural selection *No mutation No migration If assumptions are met,population will be in genetic equilibrium

Law of Genetic Equilibrium Assumptions ❖ Large population ❖ Random mating ❖ No natural selection ❖ No mutation ❖ No migration If assumptions are met, population will be in genetic equilibrium. Hardy-Weinberg law

Law of Genetic Equilibrium Hardy-Weinberg law >Allele frequencies do not change over generations. Genotypic frequencies will remain in the following proportions: p+q=1 frequency of AA r+2p9+q=1 21pq： frequency of Aa frequency of aa

➢ Allele frequencies do not change over generations. p＋q＝1 p 2＋2pq＋q 2＝1 p 2 : frequency of AA 2pq: frequency of Aa q 2 : frequency of aa Law of Genetic Equilibrium Hardy-Weinberg law ➢ Genotypic frequencies will remain in the following proportions:

例：上海人群的MN血型分布（共1788人） M血型：397人（基因型虹MLM 调查结果 MN血型：861人（基因型LML) N血型：530人（基因型虹NLy 根据调查结果及基因频率与基因型频率的关 系计算基因频率 39711 p=i+2m788 861 =0.46 1788 g=【sN= 861 =0.54

例：上海人群的MN血型分布(共1788人) M血型：397人(基因型LMLM) MN血型：861人(基因型LMLN) N血型：530人(基因型LNLN) 1788 530 861 1788 + × 1 2 ＝0.54 1 2 q＝ fNN+ fMN ＝ ＝0.46 1788 397 861 1788 + × 1 2 1 2 p＝ fMM+ fMN ＝ 根据调查结果及基因频率与基因型频率的关 系计算基因频率： 调查结果