分子生物学chapter 8

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1、Chapter8DNAReplicationChapter8DNA复制DNAReplicationGeneticinformationisalsopassedfromgenerationtogeneration.Acrucialpropertyoflifeisthateventhemostcomplexorganismsareabletobecopied.Whenoneofyourcellsdividesbymitosis,forexample,itmakestwonewcellsthatareessentiallyperfectreplicasoftheparentcell.遗传信

2、息也从一个世代到另一个世代进行传递。生命至关重要的特性是：即使是最复杂的生命也能够被复制出来。例如，当你的细胞进行有丝分裂时，它能产生两个本质上是母细胞完美复制品的新细胞。basicconceptDNAreplication:亲代dsDNA在DNA聚合酶的作用下，分别以ssDNA为模板，聚合与自身碱基互补配对的游离的dNTP，合成出两条与亲代DNA完全相同的子代DNA分子的过程。Replicon（复制子）AunitofthegenomeinwhichDNAcontainaregionfromorigintoterminatorReplisome(复制体)Themultiprotein(a

3、bout30)structurethatassemblesatreplicatingforktoundertakesynthesisofDNA.8.1GeneralfeaturesofDNAreplication8.1Semi-ConservativeReplication/半保留复制Semi-conservativereplication:AstyleofDNAreplicationinwhichproducesaDNAwithonestrandfromtheparent,andonenewlysynthesizedstrand.半保留复制：一种DNA的复制方式，产生的DNA中一条链

4、来自于母本、另一条链是新合成的。8.2InitiationofReplication/复制的起始OriCtwocriticalrepeatedmotifs:initialsite:13-mermotif,repeatedthreetimes,ssDNAformationduringinitiation.bindingsite:9-mermotifforDnaA,repeatedfourtimesatoriC.8.2InitiationofReplication/复制的起始E.colireplicationbeginsatasitecalledtheOriCReplicationdirec

5、tionNewDNAenlongationfrom3’→5’direction磷酸基团间的强负电性使dNTP难以聚合，5’端碱基配对困难.Errorbasepairing….repairBidirectionalReplication/双向复制DNA的双向复制（Replicationisbidirectional）Thefirstissueconcernstheoriginofreplication.WherealongthechromosomeisDNAreplicationinitiated?Isthereonlyasingleorigin,ordoesDNAsynthesisbeg

6、inatmorethanonepoint?Isapointoforiginrandomorisitlocatedataspecificregionalongthechromosome?Second,oncereplicationbegins,doesitproceedinasingledirectionorinbothdirectionsawayfromtheorigin?Inotherwords,isreplicationunidirectionalorbidirectional?Replicationfork:attheactualpointalongthechromosomewhe

7、rereplicationisoccurring,thestrandsofthehelixareunwound,creatingareplicationfork.SuchaforkinitiallyappearsatthepointoforiginofsynthesisandthenmovesalongtheDNAduplexasreplicationproceeds.Ifreplicationisbidirectional,two