医学遗传学 08基因的群体行为eng v课件.ppt

《医学遗传学 08基因的群体行为eng v课件.ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、08基因变异的群体行为PopulationGeneticsWhatisapopulationfromageneticperspective?Apopulationinthegeneticsense,isnotjustagroupofindividuals,butabreedinggroupThegeneticsofapopulationisconcernednotonlywiththegeneticconstitutionoftheindividualsbutalsowiththetransmiss

2、ionofthegenesfromonegenerationtothenext.Inthetransmissionthegenotypesoftheparentsarebrokendownandanewsetofgenotypesisconstitutedintheprogeny,fromthegenestransmittedinthegametes.Thegenescarriedbythepopulationthushavecontinuityfromgenerationtogeneration,

3、butthegenotypesinwhichtheyappeardonot.Thegeneticconstitutionofapopulation,referringtothegenesitcarries,isdescribedbythearrayofgenefrequencies,thatisbyspecificationoftheallelespresentateverylocusandthenumbersorproportionsofthedifferentallelesateachlocus

4、."GoalsofPopulationGeneticsTodescribehowthefrequencyofanallelewhichcontrolsatraitchangesovertime；Toanalyzethefactorsthatleadtochangesingene(allele)frequencies；Todeterminehowchangesingene(allele)frequenciesaffectevolutionandspeciation.WhyStudyPopulation

5、sandGeneFrequenciesGeneticvariabilitynecessaryforevolutionarysuccess;Measuringgeneticvariabilityatmanylocicancharacterizeapopulation;Variabilityofphenotypicandmoleculartraitsareanalyzed.1.VariabilityandGene(orAllelic)FrequenciesGeneticdataforapopulatio

6、ncanbeexpressedasgeneorallelicfrequencies;Allgeneshaveatleasttwoalleles;Summationofalltheallelicfrequenciesforapopulationcanbeconsideredadescriptionofthepopulation;Frequenciescanvarywidelyamongtheallelesinapopulation;Twopopulationsofthesamespeciesdonot

7、havetohavethesameallelicfrequencies.GenotypicfrequenciesItdescribesthedistributionofgenotypesinapopulation.ExampleBloodtypelocus;twoalleles,MorN,andthreeMM,MN,NNgenotypesarepossible(thefollowingdatawascollectedfromasinglehumanpopulation).Genotye#ofIndi

8、vidualsGenotypicFrequenciesMM1787MM=1787/6129=0.289MN3039MN=3039/6129=0.50NN1303NN=1303/6129=0.21Total6129DerivingGene(orAllelic)FrequenciesTodeterminetheallelicfrequencieswesimplycountthenumberofMorNallelesanddividebythetotalnumberofal