【精品英文课件】stature in adolescent twins

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1、Bimodality:Hallmarkofamajorgeneeffectonaquantitativetrait.Bimodality:Hallmarkofamajorgeneeffectonaquantitativetrait.PolygenicTraits1Gene3Genotypes3Phenotypes2Genes9Genotypes5Phenotypes3Genes27Genotypes7Phenotypes4Genes81Genotypes9PhenotypesCompl

2、exTraitModelDiseasePhenotypeCommonenvironmentMarkerGene1IndividualenvironmentPolygenicbackgroundGene2Gene3LinkageLinkagedisequilibriumModeofinheritanceLinkageAssociationCHGAgeneticvariation:RiskfactorforhypertensiveESRDinblacksJAmSocNephrol.2008Mar;19(3

3、):600-14.ChromograninApolymorphismsareassociatedwithhypertensiverenaldisease.SalemRM,CadmanPE,ChenY,RaoF,WenG,HamiltonBA,RanaBK,SmithDW,StridsbergM,WardHJ,MahataM,MahataSK,BowdenDW,HicksPJ,FreedmanBI,SchorkNJ,O'ConnorDT.“Intermediate”intimeandcausalityM

4、echanismTwinsCardiorenaldiseasetrait(laterlife)Time(decades...)Gene(fixedatconception)Twins:windowintoheritability(h2)ofanyphenotypeMonozygotic(MZ,identical)twins:BillyandBenny...VP=VG+VEh2=VG/VP=2(RMZ-RDZ)Source:GuinnessBookofWorldRecords.Totalmolecoun

5、tforMZandDZtwins01002003004000100200300400Twin2Twin101002003004000100200300400Twin2Twin1MZtwins-153pairs,r=0.94DZtwins-199pairs,r=0.60Familystudies(twinpairs,pedigrees).Famhxasariskfactor.In1stdegreerelatives:Parents,siblings.Heritability(h2):Fractionof

6、traitvarianceaccountedforbygeneticvariance.VP=VG+VEh2=VG/VPEstimateh2fromtwinpair(orpedigree)studies:TypeoftwinpairAllelesharingacrossthegenome.MZ=monozygotic=identical.100%DZ=dizygotic=fraternal~50%(onaverage),likeanysibpairQuick-and-dirtyalgorithm:h2=

7、VG/VP=2(RMZ–RDZ)WestJMed.1984Dec;141(6):799-806.Understandinggeneticandenvironmentalriskfactorsinsusceptiblepersons.WilliamsRR.Familyhistoryasariskfactorforcomplextraits.FamilyhistoryLinkage=Meioticco-segregationA2A4A3A4A1A3A1A2A2A3A1A2A1A4A3A4A3A2Marke

8、ralleleA1cosegregateswithdominantdiseaseLinkageMarkers…ThomasHuntMorgan–discovereroflinkageIdiosyncraticfeaturesofgeneticlinkage(=meioticco-segregation).Units.Metric=meioticrecombination(~50meioses/generation).Unitsofgeneticdista