交大微生物課件genetics

HowcanabacteriumchangeitselfbytakinggenesfromotherLectureLecture10-2BacterialII.ExchangeofgeneticinformationbetweenbacterialcellsChapter10BROCKBIOLOGYOFSchoolofLifeScienceandTechnology,ShanghaiJiaoTongUniversityShanghaiJiaoTong bination遺傳重ThephysicalexchangeofgeneticmaterialbetweengeneticelementsGeneticShanghaiJiaoTongMolecularEventsinHomologousbination同源重組Generalor binationGeneticexchangebetweenhomologousDNAsequencesfromtwodifferentsourcesHomologousDNAsequencesHavingthesameornearlythesamesequenceExtremelyimportantforallorganisms重要性25genesinvolvedinE.coliSeveralredundantpathways.Thereforeifonepathwayisinhibited,anothermaysupplynecessaryfunctions.有數(shù)條替代途徑備用Molecularmechanismof NickStrandResolutionofheteroduplex(SSB)single-strandedbindingShanghaiJiaoTongProcessesleadingtogenetic binationinprokaryoticcells原核生物遺傳重組的類型TransformationDonorDNA intheTransductionDonorDNAistransferredbyConjugationDonorDNAistransferredviacell-to-cellcontactanda Figure:10-TransformationDonorDNA intheTransductionDonorDNAistransferredbyConjugationDonorDNAistransferredviacell-to-cellcontactanda ShanghaiJiaoTongTransformationTransformationisaprocessbywhich DNAisincorporatedintoarecipientcellandbringsaboutgeneticchange.轉(zhuǎn)化是游離DNA進ShanghaiJiaoTong MechanismoftransformationBindingdsDNAbyamembrane-boundDNAbindingprotein.Passage單鏈結(jié)合蛋

oneofthetwostrandsintothecellwhiledegradestheotherstrand.Thesinglestrandinthecellisboundbyspecificproteins,andbinationwithhomologousregionsofthebacterialchromosomemediatedbyRecAproteinoccurs.(d)(d)Transformedcell.Ifbinationdoesnotoccur,cannotreplicateandwillbelost.ingShanghaiJiaoTongTransduction

TwokindsofGeneralizedtransduction:DNAfromanyportionofthehost esapartofthematurevirionin ceofthegenome.普遍性轉(zhuǎn)導(dǎo)Specializedtransduction:DNAfromspecificregionofthehostchromosomeisintegratedDNA

Figanyportionthehostgenome apartofthematurevirionin ceoftheFigFigDNAfromaspecificregionofthehostchromosomeisintegrateddirectlyintogenome-usuallyre someofthe ShanghaiJiaoTongsmidandsmidsaregeneticelementsthatreplicateindependentlyofthehostchromosome.Conjugationismediatedbyconjugative Conjugationiscontrolledbyasetofgeneswithinthesmidcalledthetra(fortransferregion接合質(zhì)粒的 Example: Structureof oriTsequenceistheoriginoftransferduringconjugation.Thearrowindicatesthedirectionoftransfer(thetraregionwouldbetransferred

Figure:10-traregionthegenesinvolvedinconjugativetransfer. genesprimarilyresponsibleforreplicationandsegregationoftheFsmidin growingShanghaiJiaoTongConjugation:EssentialCell-to-CellTransfer smidsduringConjugationConjugationbetweendifferentFigDirectcontactbetweentwoconjugatingbacteriaisfirstmadeviaapilus.ThecellsarethendrawntogethertoformamatingpairfortheactualtransferofDNA.靠近形成雜交對供體DNAShanghaiJiaoTongMechanismofDNAtransferDuringAmechanismofDNAsynthesisincertainbacteriophages,calledrollingcirclereplication,bestex insDNAtransferduringconjugation.可用滾環(huán) ReviewofMechanismofconjugativetransfer smidFig.10.22TheFsmidofanF+cellisbeingtransferredtoanF-recipientcell.Notethemechanismofrollingcirclereplication.F質(zhì)粒通過滾環(huán)轉(zhuǎn)移到Conjugationistriggeredbycell-to-cellcontact,atwhichtimeonestrandofthesmidDNAcircleisnickedandistransferredtotherecipient.Asthistransferoccurs,DNAsynthesisbytherollingcirclemechanism cesthetransferredstrandinthedonor,whilethecomplementaryDNAstrandismadeintheFig.10.22bFig.10.22bDetailsofthereplicationandtransferprocess.ShanghaiJiaoTongTheFormationofHfrStrainsandChromosomeMobilizationp.279SectionUndercertaincircumstances,F smidofE.colicanmobilizethechromosomefortransferduringcell-to-cell ShanghaiJiaoTongF+andHfrF+:CellspossessinganunintegratedFsmidHfr:Cellsthathaveachromosome-integratedsmid.(highfrequencyof BothF+andHfrcellsaredonorsandareunabletotakeupasecondcopyofthesmidorgenetically 10.11.1IntegrationofF smidandChromosome IntegrationofF smidintohostchromosomecanoccuratIS(forinsertionOnceintegrated, smidnolongercontrolsitsownreplication,butthetraoperonstillfunctionsnormallyandthestrainsynthesizespili.Figure:10-BreakageoftheHfrchromosomeattheoriginoftransferandthebeginningofDNAtransfertotherecipientWhenarecipientisencountered,DNAtransferisinitiatedattheoriTsite.

Afterpartofthe DNAistransferred,chromosomalgenesbegintobetransferred.BreakageoftheHfrchromosomeattheoriginoftransferandthebeginningofDNAtransfertotherecipientAftertransfer,theHfrstrainremainsgeneticallyHfrbecauseitretainsacopyofthetransferredgenes.Hfr菌株在

Breakagetypicallyoccursduringtransfer,onlypartofthedonorchromosomeis ShanghaiJiaoTong10.11.2UseofHfrStrainsShanghaiJiaoTongDetectionofarecipientthatisresistanttoanantibioticbutisauxotrophic(strr/lac-).受體對抗生素有抗性但為營養(yǎng)缺陷型Adonorthatissensitivetotheantibioticbutisprototrophicforthesamesubstance(strs/lac+).供體對抗生素敏感但為Thus,onminimalmediumcontainingtheantibiotic,onlyrecipientcellswillgrowfollowingthematingevent在含抗生ShanghaiJiaoTongFigFig10.26LaboratoryprocedurefordetectionofgeneticShanghaiShanghaiJiaoTongInterruptedmatingandgeneticmap中斷雜交方法與遺傳圖譜繪Interruptedmating:Conjugatingcellscan it Genespresentclosertothe it

entertheF-ThisExperimentprovideamethodofdeterminingtheThisExperimentprovideamethodofdeterminingtheorderofthege