生物工程-Concepter-of-Gene

TheageofcompletegenomicsequencesThemorewelearnaboutgenes,thelesssureweareofwhatagenereallyisWHATAREGENESCHAPTERTWOTheConceptoftheGeneinDevelopmentandEvolutionThehereditarynatureofeverylivingorganismisdefinedbyitsgenome,whichconsistsofalongsequenceofnucleicacidthatprovidestheinformationneededtoconstructtheorganism.每个生物体的基因组决定了该生物体的遗传特性，基因组拥有很长的核苷酸序列，能提供组建机体所需的信息。Afewfactsaboutinheritanceknownsinceancienttimes:Childrenresembletheirparents.Domesticationfollowedbyselectivebreedingtoimproveplantsandanimals.Between8000and1000B.C.赫伯特•斯宾塞（HerbertSpencer,1820-1903）：physiologicalunits查里斯•达尔文（CharlesDarwin，1809-1882）：gemmules奥古斯特·魏斯曼（AugustWeismann,1834-1914)：germplasm1.Earlygeneconcept2.Classicalgeneconcept3.Geneconceptevolutionanddevelopment4.DNAisthemaingeneticmaterial5.Molecularconfigurationofgene6.Geneconceptmultiplicity1.Earlygeneconcept1.1TheGreekInfluenceonideasofinheritanceHippocrates–“Humors”,whichcouldbealteredduringanindividualslifetimeandthereforediseasedornormal,weredrawnfromvariouspartsofthebodytothesemenandpassedontotheoffspring.This“pangenesis”theoryevenformedthebasisofDarwin’searlyideasofinheritance.Aristotle–semenproduceda“vitalheat”thatcookedandshapedthemenstrualbloodgivingitthecapacitytoproduceoffspringwiththesame“form”astheparent.Laterideasofinheritance(1600-1850)Preformationism–istheideathateachspermcontainsaminiatureperson:developmentismerelyaprocessofenlargingandmaturingthepersonalreadypresentinthespermcell.11Epigenesis–presumablyputforthbyHarvey,heldthatbodystructureswerenotinitiallypresentinthesexcells,butinsteadformeddenovo(anew).Illustrationofhomunculiinsperm,drawnbyHartsoekerin1695Laterideasofinheritance(1600-1850)11BlendingInheritance–thebeliefthatcharacteristicsofparentsblendedlikemixingredpaintwithwhitepaint:theresultsispinkpaint,andthereisnowaytoeverseparateouttheredandwhite.Exampleofblendinginheritanceusingthecolorofflowerstoshowhowaspeciescolorvariationwouldconvergeupononecolorinrelativelyfewgenerationsifitsoffspring'scolorvariationsweretrulyboundedbytheparent'scolors.1.2获得性遗传理论（InheritanceofacquiredcharactersL.B.Lamarck.1809）Natureproducedsuccessivelyallthedifferentformsoflifeonearth.Environmentallyinducedbehavioralchangesleadthewayinspecieschange.Morerecently,“epigeneticinheritance”hasbeenrepresentedasaformofthetransmissionofacquiredcharactersandthusasaconfirmation,atleastofasort,ofLamarck’smostfamousidea.1.3泛生论假说（HypothesisofthePangenesis）《VariationsinAnimalsandPlantsunderDomestication》1.4种质论（TheoryofgermplasmA.Weismann1883.）GermplasmSomatoplasmRoot,Stem,Leaf……Somatoplasm→Germplasm→Germplasm《ExperimentsinPlantHybridization》1.5遗传因子假说(HypothesisoftheinheritedfactorG.J.Mendel1866.)•生物性状由遗传因子控制•亲代传给子代的是遗传因子(A,a….)•遗传因子在体细胞内成双(AA，aa)在生殖细胞内为单（A，a）•杂合子后代体细胞内具有成双的遗传因子(Aa)•等位的遗传因子独立分离•非等位遗传因子间自由组合地分配到配子中否定了HypothesisofthePangenesis（泛生论）奠定了Theoryofparticulateinheritance提出了LawofsegregationLawofindependentassortment缺乏细胞在有丝分裂和减数分裂过程中染色体行为的有力证据。每一个遗传因子是一个相对独立的功能单位遗传因子的等位性遗传因子的纯洁性GregorMendel1822-1884MytimewillcomeTheworkwassimplytooaheadofitstime,toocontrarytopopularbeliefsaboutheredity.Mytimewillcome,Mendeloncesaid,butitwasover30yearsbeforehisworkwasappreciated.1900CarlCorrens（1864-1933）德国图宾根大学peasPrincipleofindependentsegregationErichvonTschermark（1871-1962）奥地利维也纳农业大学peasMendel'sprincipleswereindependentlydiscoveredandverified,markingthebeginningofmoderngenetics.Hugodevries（1848-1935）荷兰阿姆斯特丹大学eveningprimrosePrincipleofindependentassortmentWilhelmJohannsen(1857-1927)1909JohannsenproposedthetermgenetodescribeMendel'sfactorsofinheritance.但究竟细胞中什么结构与遗传因子相一致?细胞学与遗传学的结合为解决这一问题提供了途径。TheChromosomeTheoryofHeredity二倍体生物减数分裂后每个配子仅接受成对染色体中的一个。假定基因是染色体的一部分。第一次将遗传学和细胞学科学地结合起来为Mendel遗传规律的解释提供了细胞学证据WalterSutton(1877–1916)TheodorHeinrichBoveri(1862–1915)Boveriwasstudyingseaurchins(海胆),inwhichhefoundthatallthechromosomeshadtobepresentforproperembryonicdevelopmenttotakeplace.Sutton‘sworkwithgrasshoppers(蝗虫)showedthatchromosomesoccurinmatchedpairsofmaternalandpaternalchromosomeswhichseparateduringmeiosisandmayconstitutethephysicalbasisoftheMendelianlawofheredity.由于同源染色体的分离而实现等位基因的分离，导致性状的分离；决定不同性状的两对非等位基因分别处在两对非同源染色体上，由于同源染色体的分离、非同源染色体的独立分配，导致了基因的自由组合。必须进一步把某一特定基因与特定染色体相联系，证明基因的行为与染色体在细胞分裂中行为的平行关系转变为基因与染色体的从属关系。ThereareexceptiontoMendel’slawsIncompletedominance.×Codominance.LinkedGenes.LinkedGenesOnTheSameChromosomeExhibitDistortedMendelianRatios---In1905,WilliamBateson,EdithRebeccaSaunders,andReginaldPunnett×PgenenrationHomozygousstrainsPurpleflowerslongpollenRedflowersroundpollenF1genenrationPurpleflowerslongpollenF2genenration1528Purpleflowerslongpollen106Purpleflowersroudpollen118Redflowerslongpollen381RedflowersroundpollenPhenotypeExpectedObservedPurple,long11991528Purple,round400106Red,long400118Red,round133381Total21322132F2≠9：3：3：12.经典的基因概念Theoryofthegene(1925)•基因是染色体上的实体•基因象链珠一样，孤立地呈线状地排列在染色体上•基因是（Threeinone）功能(functionalunit)突变(mutationunit)交换(cross-overunit)“三位一体”的最小的不可分割的基本的遗传单位ThomasHuntMorgan(1866–1945)1866.-1926.经典遗传学理论3.基因概念的演变与发展3.1基因的位置效应PositioneffectAlfredHenrySturtevant(1891–