遗传学英文课件：Genetic Variation in Population.ppt

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1、LearningObjectivesThenatureandamountofgeneticvariationinhumanpopulations,andtheroleofgeneticvariationinliabilitytodisease.EthnicGroups:Caucasoid,Negroid,MongoloidGenesinHumanPopulationsStudyofdistributionandfrequencyofgenesinpopulationsreasonsfordifferentgenefrequenciesindifferentpopulation

2、s‘burdenofgeneticdisease’isrelatedtofrequencyandseverityofgeneticdisorders----toanindividualandtothepopulationasawhole.Mutationsmayormaynotresultinanexpressedphenotype.-MutationscanalterRNAexpression,processingand/orstability.Mutationsthathavenophenotypearecalledneutralmutations.Amutationis

3、astructuralchangeingenomicDNAsequenceduetoerrorsinDNAreplicationorrepair.-Mutationscanalsoaffectproteinexpression,processing,stability.Mutationscanbeinherited(genetic/germlinemutations)notinherited(somaticmutations)Mutation‘Mutations’thatarepropagatedandmaintainedinthepopulationatrelatively

4、highfrequenciesarecalledpolymorphisms.Polymorphismisdefinedastheexistenceoftwoormorealleles,wheretherarealleleappearswithafrequencygreaterthan1%inthepopulation.Mostmutationsarequicklylostfrompopulationduetodeleteriouseffects(naturalselection)orgeneticdrift(randomfluctuations).Mutationsmaybe

5、comepolymorphismsduetoselectiveadvantage(heterozygotesforhemoglobinsicklecellmutationaremoreresistanttomalaria)orgeneticdrift(foundereffect,smallgroupofindividualsfoundanewpopulation).PolymorphismsMendelianpopulationAninterbreedingpopulationofsexuallyreproducingindividualssharingacommongene

6、pool.Genepool,genotypes,andgenefrequencyGenotype:thegeneticconstitutionofasingleindividual.Genepool:thegeneticconstitutionofapopulationofagivenorganism.OR:Allthegenesofalltheindividualsinpopulationmakeupthegenepool.Genotypefrequency:f(AA)=NumberofindividualswithAA/Totalnumberofindividualsin

7、thepopf(Aa)=?f(aa)=?Genefrequency(allelicfrequency):thefrequenciesofthemembersofapairofallelegenesinapopulation.f(Allele)=Numberofcopiesofagivenallele/Sumofcountsofallallelesinthepopp=f(A)=(2×countofAA)+(countofAa)/2×totalnumberofindividualsOR:p=f(A)=f(A