21世紀(jì)是生命科學(xué)的世紀(jì)20世紀(jì)后葉分子生物學(xué)的突破性

PAGEPAGE54—簡(jiǎn)答題

第一章 緒論2120主要領(lǐng)域？答案：同；生物大分子單體的排列（核苷酸，氨基酸）導(dǎo)致了生物的特異性。三大支撐學(xué)科：細(xì)胞學(xué)，遺傳學(xué)和生物化學(xué)。研究的三大主要領(lǐng)域：主要研究生物大分子結(jié)構(gòu)與功能的相互關(guān)系，其中包括DNA之間的相互作用；激素和受體之間的相互作用；酶和底物之間的相互作用。答案：有人把它定義得很廣：從分子的形式來(lái)研究生物現(xiàn)象的學(xué)科。但是這個(gè)定義使分子生物學(xué)難以從分子角度來(lái)解釋基因的結(jié)構(gòu)和活性是本書(shū)的主要內(nèi)容。3二十一世紀(jì)生物學(xué)的新熱點(diǎn)及領(lǐng)域是什么？答案：結(jié)構(gòu)生物學(xué)是當(dāng)前分子生物學(xué)中的一個(gè)重要前沿學(xué)科，它是在分子層次上從結(jié)構(gòu)角度特別是從理學(xué)、化學(xué)和計(jì)算數(shù)學(xué)等多學(xué)科交叉的，以結(jié)構(gòu)（特別是三維結(jié)構(gòu)）和異常病理現(xiàn)象的關(guān)系。分子發(fā)育生物學(xué)也是當(dāng)前分子生物學(xué)中的一個(gè)重要前沿學(xué)科。人類(lèi)基因組計(jì)劃，被稱(chēng)21 世紀(jì)生命科學(xué)的敲門(mén)‖“人類(lèi)基因組計(jì)劃”以及“后基因組計(jì)劃”的全面展開(kāi)將進(jìn)入從分子水平闡明生命活動(dòng)本質(zhì)的輝煌時(shí)代。目前正迅速發(fā)展的生物信息學(xué)，被稱(chēng)為“21世紀(jì)生命科學(xué)迅速發(fā)展的推動(dòng)力。尤應(yīng)指出，建立在生物信息基礎(chǔ)上的生物工程制藥產(chǎn)業(yè)在21世紀(jì)將逐步成為最為重要的新興產(chǎn)業(yè)從單基因病和多基因病研究現(xiàn)狀可以看出這兩種疾病的診斷和治療在21世紀(jì)將取得不同程度的重大進(jìn)展遺傳信息的進(jìn)化將成為分子生物學(xué)的中心內(nèi)‖的觀點(diǎn)認(rèn)為，隨著人類(lèi)基因組和許多模式生物基因組序列的測(cè)定通過(guò)比較研究，人類(lèi)將在基因組上讀到生物進(jìn)化的歷史，使人類(lèi)對(duì)生物進(jìn)化的認(rèn)識(shí)從表面深入到本質(zhì)；研究發(fā)育生物學(xué)的時(shí)機(jī)已經(jīng)成熟。在21世紀(jì)，遺傳信息的進(jìn)化研究成果，將成為解決發(fā)育問(wèn)題的基礎(chǔ)，發(fā)育問(wèn)題這一難題可望獲得突破性進(jìn)展；21世紀(jì)，生物技術(shù)產(chǎn)業(yè)化的趨勢(shì)將不斷加劇基因工程技術(shù)轉(zhuǎn)基因技術(shù)和基因治療技術(shù)等將對(duì)21世紀(jì)的產(chǎn)業(yè)結(jié)構(gòu)產(chǎn)生深遠(yuǎn)的影響。當(dāng)前，生命科學(xué)基礎(chǔ)研究中最活躍的前沿主要包括：分子生物學(xué)、細(xì)胞生物學(xué)、神經(jīng)生物學(xué)、生態(tài)學(xué)，并由這些活躍的前沿引伸出諸如：基因組學(xué)、蛋白質(zhì)組學(xué)、人類(lèi)基因組計(jì)劃、后人類(lèi)基因組計(jì)劃、克隆羊、克隆魚(yú)、腦的十年、生物的多樣性等時(shí)髦的名詞和熱門(mén)話(huà)題。相應(yīng)的應(yīng)用研究或技術(shù)研究也正趨成熟并逐漸普及，如生物工程，即基因工程、蛋白質(zhì)工程、發(fā)酵工程、酶工程、細(xì)胞工程、胚胎工程等。由于生命科學(xué)與人類(lèi)生存、人們健康、社會(huì)發(fā)展密切相關(guān)，必將成為21世紀(jì)全球關(guān)注的領(lǐng)域。4.簡(jiǎn)述分子生物學(xué)的發(fā)展歷程。答案：從1847——識(shí)，而Morgan化學(xué)研究的進(jìn)展，Watson和Crick又提出了脫氧核糖核酸的雙螺旋模型，為充分揭示遺傳信息的傳遞規(guī)律鋪平了道路。在蛋白質(zhì)化學(xué)方面，繼Sumner1936利用紙1953Kendrew和Perutz利用X子氧過(guò)程中的特殊作用，成為研究生物大分子空間立體構(gòu)型的先驅(qū)。20世紀(jì)401941年，曾在摩爾根實(shí)驗(yàn)室工作過(guò)的美國(guó)遺傳的新概念（后來(lái)有所修改，40年代中期被普遍承認(rèn)，從而建立了生物化學(xué)、遺傳學(xué)。M.德?tīng)柌紖慰撕推渫聜冊(cè)?946年，美國(guó)微生物學(xué)家J.萊德伯格同E.L.現(xiàn)象。這兩項(xiàng)突破以及他們對(duì)噬菌體和大腸桿菌的一些基本研究，對(duì)分子生物學(xué)的發(fā)展起了十分重要的作用。1944DNA證明DNADNA們對(duì)DNA化學(xué)組成和晶體結(jié)構(gòu)的研究。1953425J.D.沃森和英國(guó)的──DNA雙螺旋結(jié)構(gòu)的分子模型。這一成就后來(lái)被譽(yù)為20最偉大的發(fā)現(xiàn)，也被認(rèn)為是分子生物學(xué)誕生的標(biāo)志。50年代在蛋白質(zhì)的結(jié)構(gòu)分析方面也取得了重要成果。英國(guó)生物化學(xué)家F.桑格第一次分析出含有51個(gè)氨基酸的胰島素的氨基酸順序。這一成果對(duì)準(zhǔn)確地研究蛋白質(zhì)本身結(jié)構(gòu)和功能之間的關(guān)系，以1973300多種蛋白質(zhì)的氨基酸1977DNA堿基順序的分析方法并完成了分析φχ174噬菌體DNA的全部約5400的布口刺格父子及他們的學(xué)生創(chuàng)立并發(fā)展的X佩魯茨自30年代末開(kāi)始，就系統(tǒng)地研究了血紅蛋白的結(jié)構(gòu)。1969年完成了全部641961年法國(guó)細(xì)胞遺傳學(xué)家雅各布和J.美國(guó)分子生物學(xué)家H.M.特明和D.巴爾的摩長(zhǎng)期從事腫瘤病毒研究的基礎(chǔ)上，于1970年分別獨(dú)立地發(fā)現(xiàn)雞肉瘤病毒和白血病病毒都是RNA病毒。在此基礎(chǔ)上他們發(fā)現(xiàn)了依賴(lài)于RNADNA聚合酶即反轉(zhuǎn)錄酶。反轉(zhuǎn)錄酶能使RNA鏈上的遺傳密碼反轉(zhuǎn)錄給DNA。這一發(fā)現(xiàn)不僅對(duì)某些腫瘤的病因作了分子生物學(xué)的闡明，而且動(dòng)搖了中心法則的不可逆性，成為中心法則的重要補(bǔ)充。真核細(xì)胞內(nèi)的調(diào)控機(jī)制要復(fù)雜得多，也是當(dāng)前生物學(xué)家重點(diǎn)探索的問(wèn)題之一。在此基礎(chǔ)之上，分子生物學(xué)發(fā)展的速度越來(lái)越快。一選擇題

第二章 基因的概念A(yù)DNAnucleotidemayconsistof DNA核苷酸可能有下列哪一項(xiàng)組成A?aribosesugar,aphosphategroup,andadenine.B?aphosphategroup,deoxyribose,andcytosine.C?uracil,deoxyribose,andaphosphategroup.D?deoxyribose,thymine,andahydroxylgroup.Whichisthemostaccuraterepresentationoftheorganizationlevelsofthegeneticinformationincells? 下列哪一項(xiàng)最準(zhǔn)確地代表了細(xì)胞中遺傳信息的組織水平A?genesnucleotidechromosomesgenome.B?genomegenesnucleotideschromosomes.C?chromosomesgenesnucleotidesgenome.D?nucleotidesgeneschromosomesgenome.EukaryoticcellsdifferfromprokaryoticcellsinthatonlytheformercontainA?ribosomes.B?cytoplasm.C?DNA.D?anucleus.TheprokaryoticorganismthathasbeenthesubjectofmanygeneticstudiesisA?Saccharomycescerevisiae.B?Neurosporacrassa.C?E.coli.D?Drosophilamelanogaster.WhichelementisnotfoundinamoleculeofDNA?DNA分子中發(fā)現(xiàn)？A?carbon.B?sulfur.C?nitrogen.D?oxygen.WhichisfoundinRNA,butnotDNA?RNADNA分子中出現(xiàn)？A?Phosphate.B?Adenine.C?Ribose.D?Cytosine. ThetwopolynucleotidechainsinamoleculeofDNAareheldtogetherby whattype of DNA分子中的兩條多核苷酸鏈?zhǔn)且蕾?lài)于哪一種類(lèi)型的化學(xué)鍵結(jié)合在一起的？A?Phosphodiester.B?Phosphate.C?Peptide.D?hydrogen.TheDNAthatmakesupbacterialchromosomesA?single-stranded.B?circularandsupercoiled.C?complexedwithhistones.D?alltheabove.WhichofthefollowingisaDNAbasepair?A?A-T.B?T-C.C?A-U.D?G-T.WhichofthefollowingisaRNAbasepair?A?A-T.B?A-C.C?U-C.D?U-A.TheDNAandhistoneproteinsinaeukaryoticchromosomearecompactedintostructurescalled 和組蛋白組成的結(jié)構(gòu)稱(chēng)為A?proteosomes.蛋白體B?nucleosomes.C?telomeres.端粒D?centromeres.著絲粒Inhistransformationexperiments,FrederickGriffithobservedthatvirulentstrainsofStreptococcuspneumoniaeproducedcolonies.菌落A?smooth,shinyB?rough,dryC?exceptionallylargeD?unusuallycoloredViralgenomesmaybecomposedof病毒基因組的可能組成是A?RNAB?DNAC?eitherRNAorD?bothRNAandDNA.IntheHershey-Chaseblenderexperiments,theirmajorconclusionwasthatHershey 和Chase合實(shí)驗(yàn)得出的主要結(jié)論是A?asinglegenedirectedthesynthesisofasinglepolypeptide.B?DNAwasthegeneticmaterial.C?DNAwasadoublehelix.D?thegeneticmaterialwaslocatedinthenucleusofcells.ThetypeofDNAfoundmostcommonlyinlivingcellsisthe form.DNA構(gòu)型是A?A.B?B.C?D?ZGeneslocatedinwhichregionofaeukaryoticchromosomearemostlikelytobetranscribed? 基因于真核生物染色區(qū)域時(shí)最有可能被轉(zhuǎn)錄A?centromere著絲粒.B?telomere端粒.C?euchromatin常染色質(zhì)D?heterochromatin異染色質(zhì)Anucleosideconsistsofa 核苷的基本組成是A?pentosesugarandanitrogenousbase.B?phosphategroupandanitrogenousC?pentosesugarandaphosphategroup.D?pentosesugar,aphosphategroup,andanitrogenousbaseProkaryoticchromosomesconsistmostlyofA?uniquesequenceDNAonly.B?repetitivesequenceDNAC?eitheruniquesequenceorrepetitivesequenceD?bothuniquesequenceandrepetitivesequenceTocreateakaryotype染色體, chromosomesarespreadonaslideandstained.A?interphase.B?telophase.C?metaphase.D?anaphase20AchromosomefromanunknownmicroscopicorganismisexaminedandfoundtocontainonlyuniquesequenceDNA.ThisorganismismostlikelyA?virus.B?bacterium.C?fungus.D?protozoan.Ineukaryoticcells,thegeneticmaterialisfoundintheA?ribosomes.B?nucleus.C?endoplasmicreticulum.D?cytoplasm.Griffith’sexperimentinjectingamixtureofdeadandlivebacteriaintomicedemonstratedthat(choosethecorrectanswer):明（選擇正確的答案）A?DNAisdouble-strandedB?mRNAofeukaryotesdiffersfrommRNAofprokaryotesC?AfactorwascapableoftransformingonebacterialcelltypetoanotherD?BacteriacanrecoverfromheattreatmentiflivehelpercellsarepresentTheX-raydiffractiondataobtainedbyRosalindFranklinsuggested(choosethecorrect羅莎琳德?X射線(xiàn)衍射圖像的數(shù)據(jù)表明（選擇正確的答案）A?DNAisahelixwithapatternthatrepeatsevery3.4nanometersB?PurinesarehydrogenbondedtopyrimidinesC?DNAisaleft-handedhelixD?DNAisorganizedintonucleosomesGriffithinjectedmicewithdifferenttypesofbacteria.Foreachofthefollowingbacteriatypesinjected,indicatewhetherthemicelivedordied:的細(xì)菌類(lèi)型，判斷老鼠是存活還是死亡？a. typeⅡR b. typeⅢS c. heat-killedⅢS d. typeⅡR+heat-killedⅢSA?lived lived died diedB?died lived died C?lived died lived diedD?died died lived lived二填空題1．基因敲除Geneknock-ou）即是（將特定基因失活的過(guò)程，它是研究（基因功能）遺傳學(xué)方法。2（pseudogen）因。3．在原核生物的基因表達(dá)調(diào)控中，因?yàn)闆](méi)有核膜，（轉(zhuǎn)錄）和（翻譯）是耦聯(lián)的。4．Anucleosomeiscomprisedoftwocopiesofhistones（H2A），（H2B），（H3），（H4），onecopyofhistone（H1），and（200）bpofDNA.三簡(jiǎn)答題Fromachemical（bonding）view, whyisdouble-strandedDNAsostable?從化學(xué)（鍵）DNA比較穩(wěn)定的原因答案：Hydrogenbondsbetweenbasesandhydrophobicbondsduetobasestacking堿基之間的氫鍵以及疏水的堿基堆積力。Whatis―Chargaff’sRule‖規(guī)則的內(nèi)容是什么？答案：A%=T%andG%=C%indsDNA.腺嘌呤和胸腺嘧啶的摩爾數(shù)相等，即A=T；鳥(niǎo)嘌呤和胞嘧啶的摩爾數(shù)相等，即G=C；含氨基的堿基（A和C）總數(shù)等于含酮基的堿基（G和T）總數(shù)，即A+C=G+T；嘌呤的總數(shù)等于嘧啶的總數(shù)，即A+G=C+T。SupercoilingDNArequiresenergyandallowsworktobedone.Whataretwobiochemicalfunctionsthatthispent-upenergyisusedfor?DNA中的能量的主要用于哪兩種生化作用？答案：Energycancausestrandseparationusedfor:（1）DNAreplication；（2）TranscriptionYouhaveisolatedaplasmidDNAthatisaclosedcircularmolecular1050bpinlengthwith5negativesupercoils. Whatarethelinkingnumber,helicalturns,writhe,andsuperhelicaldensity? 你分離出的質(zhì)DNA1050bp5DNA螺旋數(shù)（纏繞數(shù)T）、扭曲數(shù)、以及超螺旋密度是多少？答案：Writhe=W=-5；helicalturns=T=1050/10.5=100；L=T+W=100+（-5）=95Superhelicaldensity=σ=W/T=-5/100=-0.05Whatisapseudogene,andhowdoyourecognizeone?什么是假基因？你如何識(shí)別出假基因？答案：Psuedogenesarearedefinedbytheirpossessionofsequencesthatarerelatedtothoseofthefunctionalgenes,butthatcannotbetranslatedintoafunctional假基因是指與正?；蚪Y(jié)構(gòu)相似，DNA序列，即不能翻譯出有功能蛋白質(zhì)的基因。canberecognizedbytheoccurrenceofoneormoremutationsthatobviouslyrenderthem可以利用補(bǔ)償其功能的突變體而區(qū)分出假基因。Ineukaryoticcells,DNAispackagedintochromatin.Therepeatingunitofchromatiniscallednucleosome.被包裝成染色質(zhì)，其重復(fù)單元為核小體。Whatconstituteamononucleosome?每個(gè)核小體單元是由什么組成的？WhatistheconsequenceofDNApackagingontranscription?DNA怎樣的影響后果？答案1Amononucleosomeiscomposedof146bpofcoreDNAwrappedaroundahistoneoctamerof2copiesofeachofH2A,H2B,H3andH4.146bp核心DNA和各兩分子的組蛋H2AH2BH3、H4組成的八聚體構(gòu)成。（2）TheconsequenceofDNApackagingistoinhibittranscriptionduetotheinabilityoftranscriptionmachineryandtranscriptionfactorstogainaccesstoDNA.DNA被包裝成染色質(zhì)結(jié)構(gòu)后，會(huì)抑制轉(zhuǎn)錄。因?yàn)檫@一結(jié)構(gòu)能夠阻止轉(zhuǎn)錄機(jī)構(gòu)及轉(zhuǎn)錄因子與DNA之間的相互接近。Whichcombinationsofhistonesform“histone-fold”dimerswitheachotherinthenucleosome?在核小體中，每個(gè)組蛋白二聚體分別由哪幾種組蛋白組成？H3andH4formonedimerpair,H2AandH2Bformtheother.組蛋白H3和H4形成一個(gè)二聚體；組蛋白H2A和H2B形成另一個(gè)二聚體。ThroughX-raydiffractionanalysisofcrystallizedDNAoligomers,differentformsofDNAhavebeenidentified.TheseformsincludeA-DNA,B-DNA,andZ-DNA,andeachhasuniquemolecularattributes.DNAX-射線(xiàn)衍射分析，鑒定出了DNADNA不同的構(gòu)型即A-DNA、B-DNA、Z-DNA，每一種構(gòu)型各有其獨(dú)特的分子特征。oftheseformsisthemostcommonforminlivingcells?在活的生物細(xì)胞中，普遍存在的分子構(gòu)型是哪一種？（2）Z-DNAhasanunusualconformationresultinginmorebasepairsperhelicalturnthanB-DNA.Whatistheconformation?Doesthismoleculehaveanyfunctioninlivingcells?Z-DNA與B-DNA相比，每圈螺旋含有較多的堿基對(duì)數(shù)，請(qǐng)進(jìn)一步說(shuō)明Z-DNA具有怎樣的功能？（3）Whichoftheseformsisneverfoundinlivingcells? 現(xiàn)。答案：（1）B-DNAistheformmostcommontolivingcells.B-DNA是活細(xì)胞中DNA的普遍存在形式。（2）Z-DNAisalongandthin(about2nmwide)doublehelix,likeB-DNA.Unliketheright-handedB-DNAhowever,Z-DNAisleft-handed.Ithasanaxisthatrunsthroughtheminorgroove,andhas12basepairsperhelicalturnthatareinclined8.8°fromaplaneperpendiculartotheaxis.Incontrast,B-DNAhasanaxisthatrunsthroughthebasepairs,andhas10basepairsperhelicalturnthatareinclined2° fromaplaneperpendiculartotheaxis.ThemajorgrooveofZ-DNAisnotverydistinct,asitisthinandflattenedoutalongthehelixsurface,whilethemajorgrooveofB-DNAiswideandintermediateindepth(betweenthatofA-DNAandZ-DNA).TheminorgrooveofZ-DNAisextremelynarrowandverydeep,whilethatofB-DNAisnarrowandofintermediatedepth. IthasbeenproposedthatregionswithZ-DNAprovideastretchofleft-handedhelicalturnsthatareinvolvedinreplication,recombinationandtranscription.Stretchesofleft-handedturnsmayaidinunwindingright-handedhelicalturnsinB-DNAduringtheseprocesses.Z-DNAmayalsobemorestableunderextremeenvironmentalconditions. 與B-DNA相比，Z-DNA比較A-DNAisfoundonlywhentheDNAisdehydrated,soitisunlikelythatlengthysectionsofA-DNAwouldbefoundinlivingcells.Benzer用一般遺傳學(xué)方法測(cè)出T4rcistron中含有許多個(gè)突變子（或重組子）并且指出一個(gè)突變子的大小是1-3個(gè)核苷酸，后來(lái)證明這是科學(xué)上的一個(gè)驚人的預(yù)見(jiàn)。請(qǐng)回答：?你能說(shuō)出在當(dāng)時(shí)的條件下（沒(méi)有DNA序列分析技術(shù)，遺傳密碼還沒(méi)發(fā)現(xiàn)）1~3個(gè)核苷酸的結(jié)論。答案：基因是DNA基因內(nèi)可以較低頻率發(fā)生基因內(nèi)的重組，交換。通過(guò)大量的成對(duì)突變型的雜交，測(cè)得其最小的重組頻率為0.02%，即0.02個(gè)遺傳圖距。已知T415000.02少核苷酸：1.8×105÷1500×0.02=2.4bp因此指出一個(gè)突變子是1-3個(gè)核苷酸，暗示了三聯(lián)體密碼的存在。比較基因組的大小和基因組復(fù)雜性的不同：一個(gè)基因組有兩個(gè)序列，一個(gè)是A，另一個(gè)是B2000bp長(zhǎng)。其中一個(gè)是由400bp的序550bp40樣？（2）這個(gè)基因組的復(fù)雜性如何？DNA（1）這個(gè)基因組的大小為4000bp；（2）這個(gè)基因組的復(fù)雜性為450bpWhatevidencedowehavethatinthehelicalformoftheDNAmoleculethebasepairsarecomposedofonepurineandonepyrimidine?我們有什么證據(jù)表明在DNA分子的螺旋構(gòu)型中，在每一個(gè)堿基對(duì)中都含有一個(gè)嘌呤堿基和一個(gè)嘧啶堿基？答案：Twodifferentlinesofevidencesupporttheviewthatabasepairiscomposedofonepurineandonepyrimidine.有兩方面的證據(jù)支持在DNAWhenthechemicalcomponentsofdouble-strandedDNAfromawidevarietyoforganismswereanalyzedquantitativelybyChargaff,itwasfoundthattheamountofpurinesequaledtheamountofpyrimidines.Morespecifically,itwasfoundthattheamountofadenineequaledtheamountofthymine,andthattheamountofcytosineequaledtheamountofguanine.Thesimplesthypothesistoexplaintheseobservationswastheexistenceofcomplementarybasepairing,AononestrandpairedwithTontheotherstrand,andGpairedwithC.MoredirectphysicalevidencewasprovidedbyX-raydiffractionstudies. TheseestablishedthedimensionsoftheDNAdoublehelixandallowedforcomparisonwiththeknownsizesofthebases. diameterofthedoublehelixisconstantthroughoutitslengthat2nm. Thisistherightsizeaccommodateapurinepairedwithapyrimidine,buttoosmallforapurine-purinepair,andtoolargeforapyrimidine-pyrimidinepair.Thedouble-helixmodelofDNA,assuggestedbyWatsonandCrick,wasbasedondatagatheredonDNAbyotherresearchers.Thefactsfellintothefollowingtwogeneralcategories;givetwoexamplesofeach:(1)chemicalcomposition;(2)physicalstructure. WatsonCrickDNA雙螺旋模型，這些研究成果可以劃分為兩類(lèi)即DNA的化學(xué)組成與DNA的物理結(jié)構(gòu)。請(qǐng)?jiān)敿?xì)闡述這兩類(lèi)研究成果的具體結(jié)論。答案：Thedouble-helixmodelofDNAsuggestedbyWatsonandCrickhadtoincorporateexistinginformationaboutitschemicalcompositionandphysicalstructure.Intermsofitschemicalcomposition,itwasknownthatDNAiscomposedofpolynucleotides,that(A)=(T)and(G)=(C)(Chargaff'srules),andthatwhilethepercentGCvariesbetweenorganisms,theA/TandG/Cratiosdonot.Intermsofitsphysicalstructure,thestructureandmoleculardimensionsofthecomponentmolecules(thebases,sugars,phosphates)wereknown. ItwasalsoknownfromstudiesofFranklinandWilkinsthatthemoleculeisorganizedinahighlyordered,helicalstructure,andthattherearetwodistinctiveregularitiesat0.34and3.4nmalongthemolecule'saxis.化學(xué)組成即DNA堿基組成的Chargaff規(guī)則：腺嘌呤和胸腺嘧啶的摩爾數(shù)相等，即A=T；鳥(niǎo)嘌呤和胞嘧啶的摩爾數(shù)相等，即G=C；含氨基的堿基C）總數(shù)等于含酮基的堿基T）總A+C=G+TA+G=C+TDNA異性。物理結(jié)構(gòu)：DNA分子是由核苷酸組成，核苷酸有含氮的堿基、戊糖、磷酸構(gòu)成。根據(jù)富蘭克林和威爾金斯的x射線(xiàn)衍射圖像表明：DNA分子是一個(gè)十分有序的雙螺旋結(jié)構(gòu)，每?jī)蓚€(gè)相鄰堿基平面的垂直距離是3.4?，每個(gè)螺旋包含10個(gè)堿基對(duì)。Hershey-Chase32P只標(biāo)記在DNA35S只標(biāo)記在35S35S標(biāo)記的32P標(biāo)記的噬菌體重復(fù)實(shí)驗(yàn)，那么在子代病毒中是否可以找到帶32P標(biāo)記的病毒？答案：因?yàn)镈NA32P只標(biāo)記在DNA35S只標(biāo)記在蛋白質(zhì)的外殼上。35S35S因此不帶標(biāo)記。32P35P35P標(biāo)記的病毒。Theco-crystalstructureofORC（originrecognitioncomplex）boundtoDNAshowsthat200bpofDNAiswrappedin3fullright-handedturnsaroundtheyeastORCcomplex.YouassembleORContoacircular8kbplasmidcontaininganARS（autonomouslyreplicatingBeforeassembly,theplasmidhadanaverageof10negativesupercoils.Afterassembly,youextractthereactionwithphenol-chloroform,recovertheDNA,andrunitonagel.(Hint:DNAiswrappedinaleft-handedturnaroundnucleosomes).PleaseWhatisthelinkingnumber,twist,andwritheoftheplasmidafterextraction(assume10.5bp/turnofrelaxedBDNA).答案：W=-10（tennegativesupercoils）T=8000bp/10.5bpperturn=761or762L=T+W=751or752WheredoestheextractedDNAmigrateonanagarosegellackingethidiumbromide?答案：AtthepositionofsupercoiledDNA.Whatwillhappentothemobilityoftheplasmidasyouaddincreasingamountsofethidiumbromidetothegelduringelectrophoresis?Explainbriefly.SinceETBrlocallyuntwistsDNA(twistgoesdown),theplasmidwillacquirepositivesupercoils(writhegoesup).Atfirst,thiswillresultinthelossofnegativesupercoilsandtheplasmidwillmigratelessrapidly.IfyouaddenoughETBr,theplasmidwillbecomepositively supercoiledandmigrateatthepositionofsupercoiledDNA.Nowyourepeattheexperiment,butyouincludeTopoisomeraseIintheassemblyreaction.Undertheseconditions,whatisthelinkingnumber,twist,andwritheoftheplasmidafterextraction?答案：W=+3T=8000bp/10.5bpperturn=761orL=764or765The10negativesupercoilspresentintheplasmidwillbeinstantlyremovedbytopoisomeraseI,butthesolenoidalsupercoils,constrainedbyORC,willnot.AssumingthateachORCwillgenerate3positiveplectonemicsupercoils,afterproteinextraction,W=+3,T=761(sinceDNAalwaysadoptsthemostfavorablevalue),L=T+W=764.Inadditiontojuststatingthenameofthestrain,wewerelookingforatleastsomeexplanationofhowitwouldwork.選擇題

第三章 DNA復(fù)制ThroughtheirexperimentswithDNAfromthebacteriumEscherichiac,eselsonandStahlshowedthatDNAreplicationDNA和StahlDNA復(fù)制是A?conservative.B?semi-conservative.C?DuplicativeD?dispersive.AttheconclusionofDNAreplication,thetworesultingDNAdoubleheliceseachDNA的復(fù)DNA雙螺旋的兩條鏈分別是A?oneparentalandoneprogenystrand.B?twoparentalortwoprogenystrands.C?stretchesofprogenyDNAinterspersedwithparentalDNAalongbothstrands.D?twonewlysynthesizedstrands.DNApolymerasesareenzymesthatcopyA?DNAintoB?DNAintoRNAC?RNAintoDNAD?RNAintoRNA.TobeginDNAreplication,ashort primermustfirstbeproduced.為了能夠起始DNA的復(fù)制，一段短的 引物必須預(yù)先合成A?DNAB?RNAC?polypeptideD?histoneWhichE.coliDNApolymerasehastheabilityto―proofread‖newlysynthesizedDNAandremoveerroneousbases?在大腸桿菌中，哪一種DNA聚合酶對(duì)新合成的DNA具有校正功能，能把錯(cuò)配的堿基移去？A?DNApolymeraseIonlyB?DNApolymeraseIIIonlyC?DNApolymeraseIandIIID?allthreeDNApolymeraseshaveproofreadingabilityDuringsynthesis,allDNApolymerasesaddnucleotidesinwhichdirection?A?fromlefttorightB?from3’to5’C?from5’to3’D?inmorethanonedirectionatatimeIneukaryotes,DNAreplicationoccursduringwhichphaseofthecellcycle?A?B?G1C?G2D?MWhichofthefollowingisnotrequiredforDNAsynthesisreactions?A?dCTPsB?templateDNAC?DNApolymeraseD?calciumionsDNApolymerasecatalyzestheformationofaphosphodiesterbond betweenA?5’phosphateanda5’hydroxylgroup.B?3’phosphateanda5’hydroxylgroup.C?5’phosphateanda3’hydroxylgroup.D?3’phosphateanda3’hydroxylgroup.Thesequenceofnucleotides inonestrandofDNAis 5’-CCACTGG-3’,WhatisthesequenceofthecomplimentarystrandofA?5’-CCACTGB?3’-CCACTGC?5’-GGTCACC-3’D?3’-GGTGACInbacteriasuchasE.coli,replicationofthechromosomeisA?semidiscontinuousandbi-directional.B?discontinuousandunidirectional.C?continuousandbi-directional.D?semidiscontinuousandunidirectional.The3’5’exonucleaseactivityassociatedwithDNApolymerasereducesthefrequencyofreplicationerrorstoA?1/10.B?1/1,000.C?1/1,000,000.D?1/1,000,000,00.TheproofreadingactivityofDNApolymeraseremoveserrant nucleotidesfromthe ofastrand.A?3’endB?5’endC?3’and5’endD?middleOntheE.colichromosome,oriCA?encodesDNApolymeraseI.B?isabindingsiteforhistoneproteins.C?isthestartsiteforD?encodesanRNAprimer.TheenzymethatunwindsthedoublehelixtofacilitatereplicationisA?3’5’B?DNAhelicase.C?DNApolymerase.D?topoisomerase.WhentheDNAdoublehelixisreplicated,thenewlysynthesized5’ 3’strandisconsideredthe strand.A?B?laggingC?templateD?discontinuousSynthesisofthelaggingstrandA?continuously.B?conservatively.C?discontinuously.D?semidiscontinuously.WhichtypeofDNAisduplicatedbyrollingcirclereplication?A?bacteriophageλB?plasmidDNAC?bacteriophageΦX174D?alloftheaboveManytypesofmammaliancancercellsarenotablefortheirA?telomeraseactivity.B?lackoftelomeraseactivity.C?lackoftelomeres.D?increasednumberoftelomeres.TodeterminethenumberofreplicationsitesinE.coliandwhetherreplicationisunidirectionalorbidirectional,youexaminedtheresultsoftwodifferentexperiments.BothexperimentsinvolvedgrowingE.coliinamediumcontainingradioactivethymidine.Whatdidtheadditionofthymidinetothemediumallowyoutoobserveinbothexperiments? DNA什么？A?ThedifferencebetweentheleadingDNAstrandandthelaggingDNAstrand.B?ThedifferencebetweenthereplicatedandunreplicatedportionsofDNAC?ThedifferencebetweentheRNAprimerandthenewlysynthesizedDNA.ThedifferencebetweenthereplicationforkandthenewlysynthesizedDNA.D?Noneoftheabove.Basedontheexperimentsinthisactivity,whichofthefollowingistrueaboutE.colireplication?根據(jù)DNA復(fù)制的描述，下列那一項(xiàng)是正確的？A?Replicationbeginsatasinglesiteonthechromosome.B?Replicationisbidirectional.C?Synthesisbeginsatspecificsitesonthetemplatestrand.D?Alloftheabove.Duringreplication,proofreadingofthenewlysynthesizedDNAisperformedbyA?RNApolymeraseB?reversetranscriptaseC?topoisomeraseD?DNApolymerase尿嘧啶糖苷酶的功能是A?去除嘧啶二聚體B?切除RNA分子中的尿嘧啶C?切除DNAD?切除DNA分子中的尿苷酸E?切除RNA分子中的尿苷酸 DNADNA白質(zhì)？A?DNA聚合酶Ⅰ、引發(fā)酶、SSB和連接酶B?SSB、解鏈酶、和拓?fù)洚悩?gòu)酶C?連接酶、DNA聚合酶Ⅰ和ⅢD?DNASSBEDNA聚合酶ⅡDNA復(fù)制的幾種酶的作用次序是A?DNA解鏈酶→引發(fā)酶→DNA聚合酶→DNA連接酶→切除引物的酶B?DNAC?引發(fā)酶→連接酶→切除引物的酶D?DNA聚合酶E?DNA連接酶→切除引物的酶將兩段寡聚脫氧核苷酸片段和與DNA聚合酶一起加到含dGTPdCTPdTTPA2C∶1TB?1G∶1TC?3G∶2TD?E?5T∶4G∶3C∶1A噬菌體Φx174的基因組是一個(gè)由5386個(gè)堿基組成的單鏈DNA，該基因組編碼有種不同的蛋白質(zhì)，這些蛋白質(zhì)約有2380能力。對(duì)這種現(xiàn)象最好的解釋是A?它的基因組含有重疊基因B?氨基酸由二聯(lián)體密碼編碼C?細(xì)胞核糖體翻譯它的每一個(gè)密碼子不止一個(gè)D?蛋白質(zhì)在使用后即被后加工二填空題DNA復(fù)制的方向是從端到端展開(kāi)。維持DNA復(fù)制的高度忠實(shí)性的機(jī)制主要有聚合酶的高度選擇性（DNA校正功能）和（錯(cuò)配修復(fù)。端聚酶由和（蛋白質(zhì)）兩個(gè)部分組成，它的生理功能是（維持端粒的完整。染色體中參與復(fù)制的活性區(qū)呈Y型結(jié)構(gòu)，稱(chēng)為（復(fù)制叉三簡(jiǎn)答題Explainthefollowingtermsandconcepts：請(qǐng)解釋下列術(shù)語(yǔ)或概念：leadingstrandandlaggingstrand前導(dǎo)鏈和滯后鏈；Sigmafactorandholoenzymeσ因子與全酶。strandistheDNAstrandthatsynthesizedinthe5′to3′directionastheparentalduplexisunwound.ItisprimedonetimeduringsynthesisandusestheDNAstrand3’to5’astemplate.前導(dǎo)鏈?zhǔn)侵鸽S著親本雙螺旋的解開(kāi)而按照5′3′方向連續(xù)合成的DNA子鏈，以方向的親本鏈為模板。LaggingstandusestheDNAstrandthatruns5’to3’astemplateandsynthesisDNAnon-continuouslyasOkazakifragment.It'ssynthesisrequiresmultipleprimingevents.Aseriesofthesefragmentsaresynthesized,each5′–3′;thentheyarejoinedtogethertocreateanintactlaggingstrand.滯后鏈?zhǔn)侵敢?′3′方向的親本鏈為模板，不連續(xù)合成一系列5′3′方向?qū)槠瑪?，然后連接成一條完整的子鏈DNA。滯后鏈的合成需要若干次引發(fā)事件的發(fā)生。SigmafactorandholoenzymeSigmafactorisacomponentofthebacterialRNApolymeraseholoenzymewhichiscomposedofRNAcoreenzymeandSigmafactor.Sigmafactorisresponsibleforpromoterrecognitionandtranscriptioninitiation,whileRNAcoreenzymeisresponsibleforRNAsynthesis.σisaSpecificityFactor，whichdirectsthecoretotranscribespecific因子是RNA聚合酶全σσRNA核心酶負(fù)責(zé)RNA的合成。是一種特異性因子，能夠指導(dǎo)核心酶轉(zhuǎn)錄特異的基因。Whatisthetemplateusedbytelomerasetoaddtelomericrepeatsattheendsofchromosomes?端粒酶在向染色體末端添加寡聚重復(fù)單元時(shí)，以什么為模板？TelomerasecarriesitsownRNAtemplateforpolymerizationofthetelomereDNArepeats.Thatmeanstelomeraseisareversetranscriptase,i.e.anRNA-dependentDNApolymerase.端粒酶以自身攜帶RNADNARNADNA聚合酶。3．AspaceshiplandsontheEarthcarryingasampleofextraterrestrialbacteria.YouareassignedthetaskofdeterminingthemechanismofDNAreplicationinthisorganism.Yougrowthebacteriainunlabledmediumforseveralgenerations,thegrowitinpresenceof15Nforexactlyonegeneration.YouextracttheDNAandsubjectittoCsClcentrifugation.Thebandingpatternyoufindisasfollows:在利用飛船進(jìn)行科DNA有標(biāo)記的培養(yǎng)基上生長(zhǎng)幾代15N標(biāo)記的培養(yǎng)基中準(zhǔn)確地繁殖一代DNA并進(jìn)行CsClItappearstoyouthatthisevidencethatDNAreplicatesinthesemiconservativemanner,butyouarewrno.rohy?Whatotherexperimentcouldyouperform(usingthe15N15N14N14N ExperimentalsamplesamesampleandtechniqueofCsClcentrifugation)thatwouldfurtherdistinguishbetweensemiconservativeanddispersivemodesofreplication?根據(jù)這一結(jié)果，你認(rèn)為DNA行復(fù)制，但你的觀點(diǎn)是不正確的，為什么？請(qǐng)你設(shè)計(jì)另一個(gè)實(shí)驗(yàn)方案（手段即CsCl梯度離心）能夠有效地將半保留復(fù)制和彌散復(fù)制這兩種復(fù)制方式區(qū)分開(kāi)來(lái)。TheCsClcentrifugationresulteliminatesthepossibilityoftheconservativemodelofreplication,butisstillconsistentwitheithersemiconservativeordispersivemodelsofDNAreplication.TodistinguishbetweenthesetwopossibilitiesusingthesamesampleandthetechniqueofCsClcentrifugation,onecoulddenaturetheDNA,andthensubjectthesingle-strandedsampletoCsClcentrifugation.ThiscouldbedoneinpracticebyusinganalkalineCsClgradient,asthetwoDNAstrandswilldenatureathighpH.Theexpectedresultsareshownbelow.CsCl梯度離心的結(jié)果雖然排除了全保留復(fù)制的可能性，但不能根據(jù)這一結(jié)果就可證明DNA相同的技術(shù)手段即CsCl梯度離心將半保留復(fù)制和彌散復(fù)制區(qū)分開(kāi)來(lái)的方法是將DNA樣品變性，然后利用堿性CsCl梯度離心技術(shù)對(duì)單鏈DNA則出現(xiàn)一條帶，如下圖所示：

半保留復(fù)制變性后離心半保留復(fù)制變性后離心彌散復(fù)制變性后離心變性后離心彌散復(fù)制變性后離心KornbergisolatedDNApolymeraseⅠfromE.coli.DNApolymeraseⅠhasanessentialfunctioninDNAreplication.WhatarethefunctionsoftheenzymeinDNAreplication?科恩伯格從大腸桿菌中分離出了DNA聚合酶Ⅰ，在DNA聚合酶Ⅰ在DNA復(fù)制過(guò)程中具有什么功能？答案：DNApolymeraseⅠfunctionstoremovetheRNAprimersynthesizedduringtheinitiationofDNAreplicationandreplacethisRNAwithDNA.WhenDNApolymeraseⅢ,themainsyntheticenzymeforDNApolymerization,reachesanRNAprimer,itdissociatesfromtheDNA.DNApolymeraseⅠfunctionstocontinuesynthesisoftheDNAina5’-to-3’direction.ItsimultaneouslyremovestheRNAprimerusingits5’-to-3’exonucleaseactivity,andreplacestheRNAwithDNAnucleotides.DNA聚合酶ⅠDNARNA引物的功能，并合成一段DNARNADNA聚合功能的DNA聚合酶Ⅲ在遇到RNA引物時(shí)，就會(huì)從DNA5’，3’核酸外切酶的功能切除RNA5’3’方向合成DNA。DescribethemolecularactionoftheenzymeDNAligase.WhatpropertieswouldyouexpectanE.colicelltohaveifithadatemperature-sensitivemutationinthegeneforDNAligase?請(qǐng)描述DNA連接酶的DNA生怎樣的表型效應(yīng)？答案：DNAligasecatalyzestheformationofaphosphodiesterbondbetweenthe3’-OHandthe5’-monophosphate groups on either side of a single-strand DNA gap, sealing the gap.Temperature-sensitiveligasemutantswouldbeunabletosealsuchgapsattherestrictive(high)temperature,leadingtofragmentedlaggingstrands,andpresumablycelldeath.IfabiochemicalanalysiswereperformedonDNAsynthesizedafterE.coliwereshiftedtoarestrictivetemperature,therewouldbeanaccumulationofDNAfragmentsthesizeofOkazakifragments. ThiswouldprovideadditionalevidencethatDNAreplicationmustbediscontinuousononestrand.什么是DNA聚合酶的進(jìn)行性？如何測(cè)定一種DNA聚合酶的進(jìn)行性？答案：DNA聚合酶的進(jìn)行性是指某一種DNA解離的這段時(shí)間內(nèi)，催化了多少脫氧核苷酸的摻入。測(cè)定某一DNA特異性DNA，當(dāng)DNA聚合酶從模板上解離下來(lái)后，由于大量的非特異性DNA稀釋了原來(lái)的DNA模板，使得DNA聚合酶很難再與原來(lái)的模版結(jié)合，這樣就得到了新合成的DNA泳可大概知道片段的長(zhǎng)度。盡管DNA聚合酶催化聚合反應(yīng)既需要模板，又需要引物。但下面的單鏈DNA卻可以直接作為DNA聚合酶Ⅰ的有效的底物。試解釋其中的原因，并寫(xiě)出由DNA結(jié)構(gòu)。3’OH-TGGCTCATAGCCGGAGCCCTAACCGTAGACCACGAATAGCATTAGGp--’-5答案：由于此鏈DNA特殊的堿基組成，使得該DNA能夠形成如圖所示的莖環(huán)結(jié)構(gòu)：T A OH3’G GAGCTAACCGTAGACCACGAATAGCATTAGG5’C C GDNA3’-OHDNA的外切酶活性將末端錯(cuò)配的T水解掉而引入正確的G，然后再進(jìn)行延伸反應(yīng)，最終得到的產(chǎn)物是： T A CTCGGATTGGCATCTGGTGCTTTCGTAATCC-OH’GC C G

GAGCCCTAACCGTAGACCACGAATAGCATTAGGp5’簡(jiǎn)述維持DNA復(fù)制的高度忠實(shí)性的機(jī)制。答案：維持DNA聚合酶所具有的3’5’RNADNA復(fù)制的忠實(shí)性，因?yàn)楫?dāng)DNARNA誤。在岡崎提出DNADNA是僅僅是后隨鏈才是不連續(xù)復(fù)制，存在著很大爭(zhēng)議。顯然前導(dǎo)鏈的合成不需要不連續(xù)復(fù)制，但是許多研究者發(fā)現(xiàn)經(jīng)脈沖標(biāo)記的岡崎片段可以和親代DNADNA的兩條鏈都可以作為岡崎片段的模板。試提出一種機(jī)制解釋前導(dǎo)鏈的復(fù)制也可能產(chǎn)生岡崎片段，并設(shè)計(jì)一個(gè)實(shí)驗(yàn)證明你提出的機(jī)制。答案：前導(dǎo)鏈似乎也形成小的片斷，是因?yàn)樵谝粋€(gè)細(xì)胞中，含有微量的dUTP，它在DNA復(fù)制過(guò)程中有可能代替dTTP摻入到新合成的子鏈中，由于脫氧尿苷酸不是DNA分子中的正常核苷酸，所以體內(nèi)修復(fù)系統(tǒng)會(huì)將它除去。去除的機(jī)制是先在尿嘧啶糖苷酶的作用下切除DNA然后AP核酸內(nèi)切酶在AP位點(diǎn)將DNAAP位點(diǎn)在內(nèi)的一段DNA鏈切除，再由DNAAP核酸內(nèi)切酶的作用必然導(dǎo)致前導(dǎo)鏈形成小的DNA片斷。篩選AP核酸內(nèi)切酶缺失的大腸桿菌突變株，觀察上述現(xiàn)象是否發(fā)生。Telomeresareuniquerepeatedsequences.WhereontheDNAstrandaretheyfound?Dotheyserveafunction?端粒是一類(lèi)特殊的重復(fù)序列。端粒序列存在于DNA鏈的什么部位？具有怎樣的功能？答案：Telomeresarecharacteristicallyheterochromaticsequencesfoundattheendsofalinear,eukaryoticchromosome.Formostorganisms,thetelomericsequencesattheextremeendofachromosomearesimple,highlyrepeated,andspeciesspecific.Thesesequencesaresynthesizedbytheenzymetelomerase.Nearby,butnotattheveryendofachromosome,aretelomere-associatedsequences.Thesearerepeated,co