大二下學(xué)習(xí)分子試題2006quiz2

KeystoquizPartI:Describethefollowing10terms(3s(1)EF-itsstructurelikesitisatranslationalelongationitbindstoomewhentedwithotheKeystoquizPartI:Describethefollowing10terms(3s(1)EF-itsstructurelikesitisatranslationalelongationitbindstoomewhentedwithothesmallGTPhydrolysisallowsittotheprevioussteptriggerstranslocationoftheA-site(Afullisgivenifyouwrotethreeoutoffive slisted(2)a tispartlytRNAandpartlyitrescuesomesstalledbyprematurelyterminatedtherescueconcernsEF-Tu-SsrAbindingaddsaten-amino-acidtag tisrecognizedby(Afullisgivenifyouwrotethreeoutoffour slistedframeshift causedbyinsertionsordeletionsofoneorafewbasepairstheabovechangealtersthereadingframeofaprotein(4)itstandsuideitdirectsUridineinsertionsorhesofRNAo3regions:5'anchor,editingregion,andpoly(Afull isgivenifyouwrotethreeoutoffour slisteditstandsforAdenosineDeaminaseActingonRNAb.itconvertsAdenosinedeamination(2’)oInosinethrougha ssite-(6)RRFreferstoomerecyclingfactor,afactor heterminationtranslationinprokaryoticcells(1’).RRFcooperateswithEF-GandIF3toomesolypeptiderelease(1’).ItbindstotheemptyAsiteofthewhereitmimicsatRNA(7)U2snRNPisoneofthefivesmallnuclearribonuclearproteins,acomponentofthespliceosome(1’).AftertheformationofEarlycomplex,U2snRNPbindstobranchsite,aidedbyU2AFanddisplacingBBP(1’).ThisarrangementextrudedbranchsiteAresidue,whichisunpairedandavailabletoreactwiththeite8.Poly-Apolymerasemediatesheterminationoftranscriptioneukaryotes(1’).Itaddsabout200Astothe3’endofthenewlysynthesizedmRNA emplate(2’).9.Grefactorsstimulatehydrolyticediting,aproofreadingprokaryotictranscription(2’).Theyalsoserveaselongationstimulatingfactors10.Cre-loxisasimpleite8.Poly-Apolymerasemediatesheterminationoftranscriptioneukaryotes(1’).Itaddsabout200Astothe3’endofthenewlysynthesizedmRNA emplate(2’).9.Grefactorsstimulatehydrolyticediting,aproofreadingprokaryotictranscription(2’).Theyalsoserveaselongationstimulatingfactors10.Cre-loxisasimpleexamplebinationbythebinasefamily:binationsitesontheCreisanenzymeencodedbyphageP1,andloxsitesareDNA(2’).OnlyCreproteinandtheloxsitesareneededforcompleting(1’).Cre-loxiswidelyusedasatoolingeneticengineering.Part1.WhatistherelationshipnDNAandion?Whichmechanismsareerror-free,andwhichareerror-prone?Istheerror-pronemechanismuseful?(10 TherelationshipbetIfDNAdamage/lenDNAand isnotrepairedbeforethenextroundofreplication,it ionbecausetheincorrectnucleotidescouldbe onewlysynthesizedDNAbecauseofthedamagedDNAstructure.InanotherioncouldberesultedfromDNA.Error-freerepairmechanismsincludeMismatchrepair(1’),DirectreversalofDNAdamage(e.g.photoreactivation,methyltransferase,etc.)(1’),Baseexcirepair(1’),Nucleotiderepair(1’)binationrepair(1’)DNAsynthesisError-pronerepairmechanismreferstotheTheerror-pronerepairmechanismDNAsynthesis)isuseful.Itisfail-safetallowsthereplicationmachinerytobypassthedamagedAlthoughthisrepairmechanismtendsroduce ions,itsavesthecellstheworsefateof yreplicatedchromosome(chromosomebroken).2.WhataresiblecausesofdoublestrandedbreaksinE.colicells?HowE.colirepairthiskindofdamage?(10 siblecausesofdoublestrandedbreaksinE.Ionizingradiationandotherdamagingagents(reactiveoxygenspecies)directlybothstrandsofDNAerferingwiththeprogressofareplicationfork(anunrepairednickor templatestrand)indirectlycausesdoublestranded ThewaystE.colirepairsdoublestrandedbinationviatheDSB-repairpathway(majormechanism):brokenDNAretrievessequenceinformationfromthesisterchromosome. Nonhomologousendjoining(NHEJ):thetwoendsofthebrokenDNAaredirectlyjoinedtoeachotherbymisalignmentnsinglestrandsprotrudingfrombroken(TheabovewasthetTAusedtograde.Prof.Zhang t3 areassignedtoanswerthecausesofDSB,and7posareassignedtoanswertheRecBCDrepairpathwayinE.coli.Answerofnonhomologousendjoiningwillbeawardedto1poatmost.這題主要是test大家是不是熟練掌握了細(xì)菌里的RecBCD修復(fù)機(jī)制)3.Whatarethethreeprincipleclassesofablebroken(TheabovewasthetTAusedtograde.Prof.Zhang t3 areassignedtoanswerthecausesofDSB,and7posareassignedtoanswertheRecBCDrepairpathwayinE.coli.Answerofnonhomologousendjoiningwillbeawardedto1poatmost.這題主要是test大家是不是熟練掌握了細(xì)菌里的RecBCD修復(fù)機(jī)制)3.Whatarethethreeprincipleclassesofableelements?Whodiscoveredition?Whatdoyoulearnedfromtheresearchcareerofdiscoveredition?(10 ThethreeprincipalclassesofableDNAons;Viral-likeons(LTRons);2’Poly-Aretrotrans ons(nonviralretrotrans BarbaraMcCl ockdiscoveredtransablehelate Thisisanopenquestion,sojustwritedownyourownopinions(e.g.perseverance,erest,hard-working,4.Pleasedescribehowthetranscriptioninbacteriaisinitiated,elongatedterminated?(10(1)Initiation(4’):TheinitiationfactorσrecognizesandbindstopromotercaseofE.coli,themostcommonσfactortcontainstwo:-35and-10regions.Bindingoftheσfactor esRNApolymerasebindthepromoterDNA,whichformsaclosecomplex,thenthepromoterismeltedtoformtheopencomplex,andsynthesisofRNAisthenstarted.RNAusuallyhastosynthesizeseveralshortRNAsbeforefromtheregiontoentertheelongationphase.Promoter requirestheσfactorfromthecoretionof(2)Elongation(3’):RNApolymerasesynthesisRNA,unwindsDNAinre-annealsitbehind,tethegrowingRNAchain.Inaddition,RNAcarriesouttwoproofreadingfunctionsaswell.RNApolymerasecatalyzestheremovalofoneincorrectlyinsertedribonucleotidebyreincorporationofPPi,pyrophosphorolyticediting.RNApolymerasesobacktracksbyoneornucleotidesandcleavestheRNAproductstimulatedbyGrefactors,calledhydrolytic(3)Termination(3’):TranscriptioninbacteriacanbeterminatedbyRho-independentorRho-dependentmechanism.Rho-independentterminationrequirestheterminatorscontainashortinvertedrepeatrichinGandCfollowedbyastretchofabouteightA:Tbasepairs.Aftertheterminatortranscription,themRNAcanformastronghairpinstructurefollowedbyastretchofweakA:UbasepairswithitsDNAandmRNAeasilytesfromtheDNAtemplate.Rho-dependentrequiresrinsicterminatorRNAstructurebutrequiresRhotusesenergyderivedfromATPhydrolysistostop[Notes:(1)Somestudentsstillconfusedthesoftranscriptionandtranslation,wellasthebacterialtranscriptionandeukaryotictranscription.Forexample,CTDtailswasmentionedwhenexplainingtheinitiationofbacterialtranscription.Studentsusuallydonotknowhowtoongation.Andmost[Notes:(1)Somestudentsstillconfusedthesoftranscriptionandtranslation,wellasthebacterialtranscriptionandeukaryotictranscription.Forexample,CTDtailswasmentionedwhenexplainingtheinitiationofbacterialtranscription.Studentsusuallydonotknowhowtoongation.Andmostofstudentstheproofreadingsin5.PleasedescribethefeatureandbiologicalrolesoftheCTDtailofRNAⅡ.(10ThefeatureoftheCTDtail(2’):ThelargestsubunitinRNApolymeraseIIhascarboxy-(CTD),whichconsistsofmultiplerepeatsofasequenceof7aminoacids.TheCTDcanbehighlyphosphorylatedonserineorthreonineresidues.Roles(1)Duringpromoter,phosphorylationoftheCTDbythekinaseactivityTFIIHmayhelpthepolymeraseleavebehindthepromoterandGTFsandenterelongationphase.(3’)(2)Duringtranscriptionelongationandsing,manyelongationfactorsandprofessingproteinsareloadedtopolymerase,nascentmRNAand/ormachinerythroughtheCTDtails.Therefore,throughtheCTDtail,synthesissingofthenewmRNAsarehighlycoupledandcoordinatedtoensureproductionofhighqualitymRNAfortranslation.(Note:區(qū)分真核和原核。題目中指明為RNAPⅱ,說明為真核生物。另外原核生物polCTD稱為α-CTD.很多學(xué)生回答CTDtailup-element作用，這6.Whatarethechemistryandmechanismofthespliceosome-mediatedgroupronsplicingandgroupronsplicing?(10 Spliceosome-mediatedsplicingofmRNAChemistry(2’):splicingoccursastwosequentialester-transferthe2’OHofthebranchAattacksthephosphorylgroupofaconserved5’Gat5’ite,hefreeof5’exonfromron.Then,the3’OHoffree3’endof5’exonattacksaphosphorylgroupatthe3’ite,ligationofthe5’and3’exonsandreleaseofalariatformofMechanisms(4’):Step1,formationoftheE(early)complexbyrecognitionofthe5’spliiteandAbranchpo byU1snRNP,U2AFandBBPrespectively.ite,Step2,U2snRNPbindtothebranchsitetoreplaceBBPformsAcomplex.base-pairingnU2snRNAwiththebranchsitemaketheconservedAresiduethebranchsiteextrudedfromthepairedregion,andthusthisAisreadytocarrythenucleophileattack.Thetri-snRNPU4/U6/U5joinsandAcomplexisarrangedtocomplexinwhichthethreespli itesarebroughttogether.snRNPsareheldtogethertightlybyextensivebase-pairingStep3,U1leavesthecomplex,andU6occupiesthe5’hiscomplexnU4anditebybase-U4leavesthecomplex,allowingtheRNAcomponentsofU2andU6tobasepairproducetheactivesite.ThebranchsiteAattacksthe5’ite,the3-junctionandCcomplex.The5’itethenattacksthe3’ ite,freeingronlariatandthemRNAGroupronsplicing(2’):thechemistryisthesametofspliceosome-mediatedmRNAsplicing,butU4leavesthecomplex,allowingtheRNAcomponentsofU2andU6tobasepairproducetheactivesite.ThebranchsiteAattacksthe5’ite,the3-junctionandCcomplex.The5’itethenattacksthe3’ ite,freeingronlariatandthemRNAGroupronsplicing(2’):thechemistryisthesametofspliceosome-mediatedmRNAsplicing,butthesplicingiscatalyzedbyRNAitself,whichisalsonamedGroupronChemistry:the3’OHofanexogenousGnucleotideornucleosideattacksthe5’sitetoundergoester-transferreaction.Thenthe3’OHofthe5’exon5’phosphateofatthe3’ite, hereleaseofaronligatedexons.Thesplicingiscatalyzedbythe ronRNAitselfasthegroupII:7.Whatisalternativesplicing?Whatisthebiologicalimportanceofsplicing?Howalternativesplicingisregulated(Notetheinvolvementoftheelementsandingfactors)?(10Alternativesplicing(3’):manyprotein-encodedgenesinhigherronsandcanbesplicedinalternativewaystogeneratetwomoredifferentBiologicalfunctions(2’):Alternativesplicingallowsindividualgenestoproducemultipleproteinisoforms,therebyplayingacentralpartinexpandingdiversityfromalimitednumberofgenesandregulatinggeneexpreseukaryotes(2’).Alternativesplicingalsohasalargelyhiddenfunctioniningenecontrol,ingRNAsfornonsense-mediateddecay.Regulatorymechanisms(5’):alternativesplicingisregulatedby factors(activatorsortrecognizeanarrangementitivenegative ingsequenceelementscalledexonicronic)splicingorsilencers.layningandingmodulatesthesplicingofregulatedexons.ActivatorsincludemembersoftheSRproteinfamilyandcanactivatesplicingbybindingtoexonsplicingenhancersusingRNA-andrecruitingthesplicingmachineryusing frequently ribonucleoprotein(hnRNP)family,whichbindtoronicsplicingblockingspecific[Note:有些同學(xué)不懂什么是ing，什么是ing；還有的同學(xué)回答trans-splicing的機(jī)制。Hereissomeadditionalmaterialto heelementsandingfactors.ThebasicconceptforhowtranscriptioncontrolledinbacteriawasprovidedbytheclassicformulationoftheforofgeneexprestypesofsequenbyJacobandMonodin1961.TheydistinguishedninDNA:tcodeforingproducts;ingtfunctionexclusivelyheDNA(andalsoRNAinoursplicingcase).Geneactivityisregulatedbytheeractionsofthe(usuallysitesingproducts(usuallyproteins)withtheingoreformalAgeneisasequenceoftcodesforadiffusibleproduct.Thismaybeprotein hecaseofthemajorityofgenes)ormaybeRNAheoftcodefortRNAandrRNA).Theinoursplicingcase).Geneactivityisregulatedbytheeractionsofthe(usuallysitesingproducts(usuallyproteins)withtheingoreformalAgeneisasequenceoftcodesforadiffusibleproduct.Thismaybeprotein hecaseofthemajorityofgenes)ormaybeRNAheoftcodefortRNAandrRNA).Thelfeaturetthediffusesawayfromitssiteofsynthesistosewhere.Anygenetistodiffuseawayfrom tmadeittofunctionelsewhereisdescribedThedescriptioning stoanysequenceofDNA/RNAexclusivelyasaDNA/RNAsequenceinsitu,affectingonlytheDNA/RNAtowhichitisphysicallylinked GENEVIII]8.Whatarethechallengesoftranslationofeticinformationoaprotein(4s)?Whatarethefourcomponentsoftranslationmachinerys)?Pleasedescribetherolesofeachranslation(rememberrelationshipTranslationnthestructureandfunction)(12 twomainchallenges(4 TTherefore,RNAcannotberecognizedbyaminoeticcodehastoberecognizedbyanadaptormoleculeandthisadaptorhasto yrecruitthecorrespondingaminoFourcomponentsoftranslationmachineryandtheirranslationMessengerRNA(mRNA)servesastheranslation(1’)The hemRNAconsistsofaseriesofthree-nucleotidelongunitscalledcodons(1’).TheprokaryoticmRNAandeukaryoticmRNAemployeukaryotes(1’).cruitthe ome--theRBSinprokaryotesandthe5'captRNAtransferRNAisthemolecularadaptornthecodonandcorrespondingamino-acid(1 ).ThetertiarystructureofthetRNAaninvertedL,inwhichtheacceptorstemandodonloopitionedthetwoextremeends.Theaminoacidsisattachedtotheacceptorstem,and