遺傳學新版課件 2

CHAPTER2ExtensionsofMendel:ComplexitiesinRelatingGenotypetoPhenotype

Overviews

1900,RediscoveryofMendelsLaw1902,WilliamBateson,EnglishversionofMendelism1909,WilliamBateson,Mendel’sPrincipleofHeredityPlants:peas,beans,sunflowers,cotton,wheat,barley,tomatoes,maizeAnimals:cattle,sheep,cats,mice,rabbits,guineapigs,chickens,pigeons,canaries,moth

1.AllelicVariationandGeneFunctionSnapdragons

a.IncompleteDominance-Partialdominance

b.CodominanceKarlLandsteiner(c)CodominantMNbloodtypeDifferentDominanceRelationshipsc.MultipleAlleles

AllelicSeriesc+＞cch＞ch＞c

AllelicSeriesc+＞cch＞ch＞cAlbino:null(amorphic)Chinchillaandhimalayan:hypomorphicPlantincompatibilitysystemsAllelicSeries

A＞at＞aA_agoutiatatblack/yellowaablackABOBloodTypes

Genotypes,Phenotypes,andFrequenciesintheABOBlood-TypingSystemEstablishthedominancerelationshipbetweenmultipleallelesPure-breedinglentilswithdifferentseedcoatpatternsmarbled1＞marbled2＞spotted=dotted＞clear

TheDominanceRelationshipd.TestingGeneMutationsforAllelismWhy?Mutationsofthesamegeneimpairthesamegeneticfunction.e.g.TestsforallelismEyecolormutationsinDrosophilae.VariationAmongtheEffectsofMutationsVisiblemutationsSterilemutationsLethalmutationse.g.Theyellow-lethalmutationinmiceGenesFunctiontoProducePolypeptidesf.GenesFunctionWhyAreSomeMutationsDominant

andOthersRecessiveRecessivemutationsareloss-of-function

alleles.Dominantmutationsaregain-of-function

alleles.g.

Dominant,Recessive,Why?FromGenotypetoPhenotype

a.InfluenceoftheEnvironment:PhysicalEnvironment:e.g.Drosophilamutation:shibire(paralysis)25℃,viableandfertile,butsensitivetoasuddenshock29℃,falltothebottomanddiePhenylketonuria(PKU),low-phenylalaninediet,withoutseriousmentalimpairment

2.GeneAction:

PatternbaldnessBiologicalEnvironment:FromGenotypetoPhenotypePenetrance(外顯率)

Expressivity（表現(xiàn)度）

Incompletepenetrance:Polydactylyb.PenetranceandExpressivityTheLobemutationinDrosophilaVariableexpressivityHapsburgjaw:

completePenetranceandVariableExpressivityEmperorMaximilanI(a)---PhilipI---CharlesV(b)---PhilipII---PhilipIII---PhilipIV(c)---CarlosII------AlfonsoXIII(d)TheEuropeanNobility

c.GeneInteractions

(a)rosecomb(b)peacomb(c)walnutcomb(d)singlecombBatesonandPunnett’sexperiment

PandR---walnut

pandr---single

CombShapeinChickens

d.Epistasis

e.g.

Drosophilaeyecolor:

cinnabar---recessive---homozygote---cinnabar

white---recessive---homozygote---white

Whiteandcinnabar---White---epistatic

e.g.SweetpeaC---PComplementaryactionpp---C,cc---PEpistatice.g.shepherd’spurseA---b,B---aEpistaticEpistasisGeneCP

Precursor---Intermediate---Anthocyanin

Genotype

C-P-+++

ccP-+--

C-pp

++-Precursor,Intermediate,andProductTwoTypesofSeedCapsulesofShepherd’sPurseInterpretationforCrossesRecessiveepistasisDominantepistasise.ComplementationBreedingstudiese.g.i

PKU:BrainimpairmentInterferemelaninpigmentCompoundsinbloodandurinee.g.ii

BristlesinDrosophila:wild-type,longsmoo