DNA复制(第一讲)

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1、ElectronMicroscopyofreplicatingDNArevealsreplicatingbubbles.Howdoesoneprovebidirectionalforkmovement?免疫学信息网http://www.immuneweb.comPulsewithradiolabelednucleotide;chasewithcoldnucleotide.Thendoautoradiography免疫学信息网http://www.immuneweb.comDNAReplicationDNAreplicationissemi-conservati

2、ve,onestrandservesasthetemplateforthesecondstrand.Furthermore,DNAreplicationonlyoccursataspecificstepinthecellcycle.Thefollowingtabledescribesthecellcycleforahypotheticalcellwitha24hrcycle.StageActivityDurationG1Growthandincreaseincellsize10hrSDNAsynthesis8hrG2Post-DNAsynthesis5hrMM

3、itosis1hrDNAreplicationhastworequirementsthatmustbemet:1.DNAtemplate2.Free3'-OHgroup免疫学信息网http://www.immuneweb.com免疫学信息网http://www.immuneweb.comDNAReplicationDNAreplicationissemi-conservative,onestrandservesasthetemplateforthesecondstrand.Furthermore,DNAreplicationonlyoccursataspeci

4、ficstepinthecellcycle.Thefollowingtabledescribesthecellcycleforahypotheticalcellwitha24hrcycle.StageActivityDurationG1Growthandincreaseincellsize10hrSDNAsynthesis8hrG2Post-DNAsynthesis5hrMMitosis1hrDNAreplicationhastworequirementsthatmustbemet:1.DNAtemplate2.Free3'-OHgroup免疫学信息网http

5、://www.immuneweb.com免疫学信息网http://www.immuneweb.comProteinsofDNAReplicationDNAexistsinthenucleusasacondensed,compactstructure.ToprepareDNAforreplication,aseriesofproteinsaidintheunwindingandseparationofthedouble-strandedDNAmolecule.TheseproteinsarerequiredbecauseDNAmustbesingle-stran

6、dedbeforereplicationcanproceed.1.DNAHelicases-TheseproteinsbindtothedoublestrandedDNAandstimulatetheseparationofthetwostrands.2.DNAsingle-strandedbindingproteins-TheseproteinsbindtotheDNAasatetramerandstabilizethesingle-strandedstructurethatisgeneratedbytheactionofthehelicases.Repli

7、cationis100timesfasterwhentheseproteinsareattachedtothesingle-strandedDNA.3.DNATopoisomerase-Thisenzymecatalyzestheformationofnegativesupercoilsthatisthoughttoaidwiththeunwindingprocess.Inadditiontotheseproteins,severalotherenzymesareinvolvedinbacterialDNAreplication.免疫学信息网http://ww

8、w.immuneweb.com4.DN