资源描述：
《microbial genetics - portland state university：微生物遗传学-波特兰州立大学》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、MicrobialGeneticsWHY?termsGenotypereferstogeneticmakeupPhenotypereferstoexpressionofthatgeneticmakeupHeritabletraitsmustbeencodedinDNAMutationsoccurrandomlyMutantsresistanttoanantibioticKindsofmutantsAuxotroph:lossofbiosyntheticenzymeCold-ortemperature
2、-sensitive:enzymefunctionisrestrictedtonarrowertemperaturerangeDrugresistanceorsensitivity:permeability,degradation,orsiteofactionMorphology:changeincapsuleorotherfeatureleadstochangeincolonyCatabolic:lossofadegradativeenzymeleadsto,forexample,inabilit
3、ytofermentacarbohydrateVirus-resistant:lossofsurfacefeaturethatisavirusreceptorResultsofpointmutationsFrame-shiftmutationsReversionsSame-sitereversion:maybetruerevertant(samesequence)orjustrestoreactivitySecond-sitereversionFrame-shiftProductionofanoth
4、erenzymethatfulfillsthefunctionMutagensAnalogsforbases5-bromo-uracilforthymine(5BUcanpairwithGaswellaswithA)2-aminopurineforadenine(2APcanpairwithCaswellaswithT)Intercalatingagents(ethidiumbromide)UV(260nm)causesdimerizationofadjacentthymines(photoreac
5、tivation)IonizingradiationcauseschemicalchangestotheDNAGenerationoffreeradicalsthatcanreactwithDNASSorDSbreaksintheDNAmoleculeTransposablegeneticelementsRecombinationRecombinationGeneticexchange:transformationGeneticexchange:plasmidtransferSmall,usuall
6、ycircular,independentlyreplicatingDNAmoleculesGenerally,G-plasmidsreplicateasdoeschromosomalDNA,G+plasmidsby“rollingcircle”replicationGenesofreplicationcontrol,timinginitiationonplasmid(ori)Someplasmidsintegrate(F+,Hfr)Mostaredouble-strandedAbout1-100k
7、bCodefor:R-factors(R-plasmids):antibioticresistance,heavymetalresistanceVirulenceplasmids:adhesins,hemolyticfactors,toxin,Ti,bacteriocinsDegradation,tol,nah,Plasmidcopy#Compatibility(inc)AveryExperimentTransformationCompetence:abilitytobetransformedSte
8、psintransformationDNAbindinganduptake(SSorDS,dependingonspecies)Integration(recA)Competencemaybeinducedbyelectroporation,CaMechanismoftransformationTransductionGeneralized—canbecarriedoutbyeitherlyticortemperatephageSpecialized—requires
