分子生物學(xué)試題庫(kù)

目錄

ChapterO-andPart-OpeningImages3

IMultipleChoice6

IShortAnswer8

2MultipleChoice12

2ShortAnswer14

3MultipleChoice18

3ShortAnswer20

4MultipleChoice24

4ShortAnswer26

5MultipleChoice29

SShortAnswer32

6MultipleChoice35

6ShortAnswer37

7MultipleChoice41

7ShortAnswer43

8MultipleChoice47

8ShortAnswer49

9MultipleChoice54

9ShortAnswer56

lOMultipleChoice60

lOShortAnswer62

UMultipleChoice65

UShortAnswer67

12MultipleChoice71

12ShortAnswer73

13MultipleChoice77

13ShortAnswer79

14MultipleChoice83

14ShortAnswer85

15MultipleChoice89

15ShortAnswer91

16MultipleChoice95

16ShortAnswer97

17MultipleChoice101

17ShortAnswer103

18MultipleChoice108

18ShortAnswer110

19MultipleChoice114

19MultipleChoice120

20MultipleChoice126

20ShortAnswer128

21MultipleChoice138

21ShortAnswer140

22MultipleChoice143

22ShortAnswer145

23MultipleChoice149

23ShortAnswer151

24MultipleChoice155

24MultipleChoice161

25ShortAnswer163

25MultipleChoice167

26MultipleChoice173

26ShortAnswer175

27MultipleChoice179

ChapterO-andPart-Opening

Images

SectionOpener1:False-coloredchromosomesofDrosophilaamericana.TheX

chromosomeismagenta,theYchromosomeisyellow,chromosome4isblue,andthe

remainingautosomesaregreen.Thelargepolytenechromosomeswereobtainedfroma

femaleheterozygousforinversionsontheXandchromosome4,formingloopswithinthe

associatedhomologs.Thesmallmetaphasechromosomeswereobtainedfromafemaleanda

malewithX-4centromericfusions.

SectionOpener2:Artist'sconceptionofareplicationfork.(Notethattheapparentextra

strandsofDNAaretheresultofloopingofthelaggingstrand;theentireloopisnotvisiblein

theimage.)

SectionOpener3:Acomputer-generatedintensitycontourmapoftheDrosophilaactivator

Bicoiddetectedbyfluorescenceconfocalimagingofasinglesliceofanucleusinanearly

embryo.

SectionOpener4:Imageofazincfingernuclease(ZFN),anengineeredenzymethatcanbe

usedtocleaveDNAatanydesiredsequence.Eachzincfingerprotein(Zninsilver)is

coupledtoaFokIendonucleasedomain(centralribbonstructures).Thezincfinger

determinesthesequencespecificity.Whentwooftheproteinsbindtotheirtargetsequence,

theFokIdomainsjoinandcreateadouble-strandbreak.

Chapter1,Opener:IllustrationofastrandofDNA.

Chapter2,Opener:Imageofthe3Dorganizationofribosomesinthecontextoftranslating

polysomes,inwhichmultipleribosomesaresimultaneouslytranslatingasinglemRNA

temple.Polysomesadoptastaggeredorpseudohelicalorganizationofribosomesalongthe

mRNA,withthetranscriptbeingsequesteredontheinside,thetRNAentrancesitesbeing

accessible,andthepolypeptideexitsitesfacingthecytosol.

Chapter3,Opene亡ImageofDNAthathasbeenseparatedbysizeonanagarosegel.

Chapter4,Opener:Thestructureofadenovirusas6Aresolution.Virusesinfecting

eukaryoticcells,liketheirhosts,haveinterruptedgenes.

Chapter5,Opener:Thegenomesequenceofoneofthemostcommonspeciesofcommensal

inourgut-Bacteroidesfragilis.Theimagedepictsmorethan4000genesinagenomeof

5,205,140basepairs.B.fragilisisthemajorcomponentofmorethan500bacterialspeciesin

ourgut-between4%and13%oforganisms.Mostofthetime,itexistswithoutcausingharm

andactuallymaybenefitusbyhelpingdigestionandpreventinggrowthofharmfulbacteria.

Chapter6,Opener:Imageofananopore,arecentdevelopmentrevolutionizinggenome

sequencing.Nanoporesequencingisafast,inexpensivetechniquetosequenceDNAasit

passesthroughtinypores.Theadvancebringspersonalized,genome-basedmedicinecloserto

reality.

Chapter7,Opener:Artist'srenderingofredbloodcellswithinanartery.Hemoglobin,the

oxygen-carryingmoleculeinthesecells,consistsofa-andp-globinchains.Botha-and0-

globinareencodedbygenescontainedinclustersofrelatedgenes.

Chapter8,Opener:PlotofgenomerearrangementforthesixMullerelements(i.e.thesix

chromosomearms)amongeightspeciesofDrosophila.Eachverticallinerepresentsasingle

geneandthelinesthatconnectthegenesbetweenthespecieshelptodeterminethemovement

ofthegeneswithinandbetweenchromosomalarmsamongthedifferentspecies.The

centromeresareindicatedwithsolidhalfandwholecircles.EachMullerelementisshownin

shadesofasinglecolor:A,red;B,green;C,blue;D,yellow;E,magenta;F,orange.Blocks

ofgenesinD.grinishawiarearbitrarilycoloredwithineachMullerelement.

Chapter9,Opener:CutawayofaviruswithDNAbeingpackagedwithin.

Chapter10,Opener:Thespatialarrangementofnucleosomes,comprisedoffourcore

histones(orange,yellow,blueandgreen)andtwoturnsofDNA(grey),restrictstheaccessof

avarietyofavarietyoffactorstoDNAsequences.Dynamicregulationofchromatin

environmentsiskeytoallprocessesinvolvingDNA,includingtranscriptionandthe

replicationandrepairofDNA.

Chapter11,Opener:Acrystalstructureat2.2AresolutionofthearchebacterialSulfalobus

solfataricusDNApolymeraseDpo4complexedwithDNA.ADNAadduct(1,N2-

ethenoguanine,yellow)ispresentatthereplicationfork,resultinginpairingofdGTP(green)

oppositethedC5'totheDNAadduct,leadingtoaframeshift.Theformationoftheframeshift

productwasestablishedusingmassspectrometry(bottomoffigure).

Chapter12,Opener:Imagesofcircularplasmids.

Chapter13,Opener:The3Dstructureofafamily51arabinofuranosidasefromClostridium

thennocellum.Arabinofuranosidasesarefoundinbacteria,fungiandplantsandplayarolein

thedegradationofhemicellulose,aclassofpolymericcarbohydratesstoredinplantcellwalls.

Chapter14,Opener:Athree-dimensionalreconstructionofatopoisomerasedetermined

usingdatafromX-raycrystallographicstudies(blueandred).Thetopoisomeraseismodeled

intheprocessofgrippingabrokenDNAduplex(showningreen)andtransportingasecond

duplex(theblue/orangerosette).

Ch15,Opener:MolecularmodelofaHollidayjunction,amovingpointofcontactbetween

twoDNAdoublehelicesthathavebeenunwoundintofourstrandsduringDNA

recombination.

Chapter16,Openei':3DreconstructionoftheDNArepairkinaseDNA-PKcsat1.3nm

resolution.

Chapter17,Opener:Astylizedscanningelectronmicroscopicimageofagenericenveloped

virus.ExamplesofsuchvirusesincludeHIVandInfluenzaviruses.

Ch18,Opener:ComputermodelshowingthemolecularstructureofaT-cellreceptor(TCR,

pinkandblue)boundtoanallogeneic(non-self)majorhistocompatibilitycomplex(MHC)

molecule(purple,greyandgreen).TCRsarefoundonthesurfaceofT-cells.Engagementof

theTCRwithanantigenresultsinactivationofitsT-cellthroughaseriesofbiochemical

events,mediatedbyassociatedenzymes,co-receptors,andspecializedaccessorymolecules.

MHCsindicatewhetheracell(orcells)isfromthesameorganismastheT-cell.Iftheyare

non-selfthenanimmuneresponseistriggeredandtheT-cellreceptorsareconfiguredto

recognizetheMHC.

Ch19,Opener:Molecularmodelshowingthesecondarystructure(helices)ofthe

transcriptionfactorBrachyury(purple)bindingtoamoleculeofDNA.Brachyurybindstoa

specificsequenceofbasesintheDNAcalledaT-box.Brachyuryhasbeenfoundtobecrucial

inembryonicdevelopmentinanimals.Itisnecessarytoformthemesoderm,theprecursor

tissuethateventuallydevelopsintotheinternalorgansandbones.

Ch20,Opener:IllustrationoftranscriptionshowingRNApolymeraseatwork.TheDNA

templateandthenascentmRNAareshown.

Ch21,Opener:UIAdaptorsareananotechnologyusedforgenesilencing-theprevention

ofproteinproductionbyaparticulargeneofinterest.UnlikeantisenseandRNAinterference

genesilencers,U1adaptorsworkalthespliceosome:macromolecularassembliesinsidethe

cellnucleusthatprocesspre-mRNAtranscriptspriortoexportintothecytoplasmand

translationintoproteins.Specifically,aUIadaptor(red)canbetailor-madetobindpre-

mRNA(blue)fromaspecificgeneandtetheritfirmlytotheUIsnRNPcomponentofthe

spliceosome,therebygumminguptheworks.Thisactionpreventstheadditionofapoly(A)-

tailtothepre-mRNA,whichleadstorapiddegradationbyRNaseenzymesandpreventsits

useinproteinsynthesis.

Chapter22,Opener:Computerartworkofaconitase(blue),incomplexwithferritinmRNA

(red).AconitaseisinvolvedintheKrebscyclebuthereitisperformingasecondaryfunction

asanironregulatoryprotein(1RP).ItdoesthisbybindingtoferritinmRNA,whichprevents

translationintotheproteinproduct(ferritin).Ferritinisanironbindingandstorageprotein

thathelpstoprotectcellsfromthetoxiceffectsofexcessiron.

Ch23,Opener:Illustrationshowingareversetranscriptaseenzymetranscribingasingle

strandofRNAintodouble-strandedDNA.Reversetranscriptaseisapolymeraseenzyme

commonlyfoundinretrovirusesthatcatalysesreversetranscription,theprocessof

synthesizingDNAfromanRNAtemplate.

Chapter24,Opener:Inallorganisms,cytosolicribosomessynthesizingmembraneor

secretoryproteinsaretargetedtoeithertheplasmamembrane(prokaryotes)orthe

endoplasmicreticulumbyacomplexofRNAandproteincalledthesignalrecognition

particle(SRP).Electronmicrographsofunstained,freeze-driedEscherichiacoliSRPs(a

samplemicrographisshowninthebackground)wereusedtoidentifyindividualparticle

imagesandtocalculateathree-dimensionalreconstructionofE.coliSRP(orangetransparent

surface).E.coliSRPwasobservedasanelongatedparticleresemblingthenumeral9.A

three-dimensionalmapoftheinternalRNAobtainedbyelectronspectroscopicimagingand

existingcrystallographicdataofindividualcomponentsanddomainswereusedtoconstructa

model(red,green,andblueribbons)forthestructureofE.coliSRP.

Chapter25,Opener:Anaminoacid(green)slithersintothechemicalreactioncenter,moving

throughanevolutionarilyancientcorridoroftheribosome(purple).Theaminoacidis

deliveredtothereactioncorebythetransferRNAmolecule(yellow).

Chapter26,Opener:Visualizationofthelacrepressorprotein(inblue)asitbindswithDNA.

TheDNAisshowninyellow,redandgreen.Thelacrepressorbindingsitesareindicatedin

purple.BybendingtheDNAintoaloop,thelacrepressorpreventstheexpressionofthe

proteinsneededtometabolizelactose.

Chapter27,Opener:AnimageofbacteriophageEpsilonl5.Thebacteriophageisshownata

resolutionof4.5A-thehighestresolutionachievedforalivingorganismofthissize.

Chapter28,Opener:ADrosophilasalivaryglandchromosomestainedsothatmethylated

histoneH4appearsred/pinkandRNApolymeraseIIappearsgreen.Notethatsitesofactive

transcriptiondonotoverlapwiththisparticularsiteofhistonemethylation(histoneH4K20).

Chapter29,Openei'：StructuralmodelofthetripartitecohesincomplexconsistingofSmc1

(red),Smc3(blue)andSccl(green)proteinsencirclingtwolOnmsisterchromatids,e.g.

DNA(gold)wrappedaroundnucleosomes(grey).

Chapter30,Opener:CrystalstructureofthepreQiriboswitchaptamerdomain(transparent

surface)fromThennoanaerohactertengcongensis.TheRNAbackboneisdepictedasapurple

tubewithassociatedbasescoloredaccordingtopositionfromthe5'?end(blue)tothe3'-end

(red).Freeandboundmetabolitemoleculesaredepictedasball-and-stickmodelswith

transparentsurfaces(pink).

ChapOl,Chapter1

MultipleChoice

1.Thecompletesetofhereditaryinformationcarriedbyanorganismisits

A.chromosome.

B.genome.

C.doublehelix.

D.gene.

E.nucleotide.

Ans:B

Page3

2.HersheyandChasetrackedDNAduringphageinfectionusingaradioisotopeof

A.oxygen.

B.sulfur.

C.nitrogen.

D.phosphorus.

E.carbon.

Ans:D

Page6

3.Theprocessofineukaryoticcellsisanalogoustobacterialtransformation.

A.transfection

B.transcription

C.transition

D.translation

E.translocation

Ans:A

Page7

4.Inapolynucleotide,aphosphategroupislinkedtothecarbonsoftwopentoses.

A.Vand2'

B.Vand3'

C.3'andS'

D.1/and5r

E.2'and3'

Ans:C

Page7

5.InDNA,thenumberoftimesonestrandcrossesovertheotherinspaceisits

A.twistingnumber.

B.positivesupercoilingnumber.

C.writhingnumber.

D.negativesupercoilingnumber.

E.linkingnumber.

Ans:E

Page9

6.IntheB-formofDNA￡

A.thetwopolynucleotidechainsaredescribedasparallel.

B.basepairslieperpendiculartothesugar-phosphatebackbone.

C.thewidthofthehelixvariesbetweenA-TandG-Cbasepairs.

D.purinebasespairwithotherpurines.

E.thereareapproximatelytwelvebasepairsperturnofthehelix.

Ans:B

Page11

7.DNAreplicationissemiconservative,meaningthat

A.oneofthetwodaughterduplexesconsistsofbothoriginalparentalstrands.

B.foreachdaughterduplex,onlyoneoftheparentalstrandsisusedasatemplateforboth

daughterstrands.

C.eachdaughterduplexmaydifferinsequencefromtheparentalduplex.

D.eachdaughterduplexconsistsofoneparentalstrandandonenewlysynthesized

daughterstrand.

E.eachdaughterduplexhassectionsoforiginalparentalduplexandsectionsofnewly

synthesizeddaughterduplex.

Ans:D

Pages12,13

8.Whichofthefollowingisatransitionmutation?

A.A-T3G-C

B.A-TBC-G

C.A-TfT-A

D.G-C玲C-G

E.G-C->T-A

Ans:A

Page18

9.Ascomparedtotheoriginalmutation,asuppressionmutationoccurs

A.inthehomologousalleleofthesamegene.

B.atthesamesite.

C.inanothernonhomologousgene.

D.inadifferentcodonofthesamegene.

E.inanothersiteofthesamecodon.

Ans:C

Page20

10.Aviroidis

A.RNAencapsulatedinprotein.

B.double-strandedDNAencapsulatedinprotein.

C.anakedDNAmolecule.

D.single-strandedDNAencapsulatedinprotein.

E.anakedRNAmolecule.

Ans:E

Page23

ShortAnswer

11.Thebasicbuildingblockofnucleicacidsisthenucleotide.Itiscomposedofthree

components.Whatarethey?

Ans:Theyareanitrogenousbase,asugar,andaphosphate.

Page7

12.Therearetwotypesofnucleicacidsincells,DNAandRNA.Listtwodifferencesbetween

thestructureofDNAandRNA.

Ans:1)DNAhasthepyrimidinebasethymine,whereasRNAcontainsuracil.2)DNAhas2'-

deoxyribose,whereasRNAhasribose.ThesugarinRNAhasan-OHgroupatthe2'position

ofthepentosering.

Page7,8

13.Ifthemole%percentageofAresiduesindouble-strandedDNAis29%,whatwouldthe

mole%ofGresiduesbe?

Ans:ThetwostrandsofDNAarecomplementarywithGresiduesononestrandpairedwith

Cresiduesontheotherstrand,andwithAresiduespairedwithTresidues.Therefore,ifthe

mole%ofAis29%,thenthemole%ofTis29%andthemole%ofG+Cwouldbe42%.

SinceGmustequalC,soasaresultthemole%ofGandofCwouldbe21%.

Page10

14.Thesizeofthesmallesthumanchromosomeis4.7x107bp.IftheDNAisintheB-form

helix,whatwouldbethelengthincmofthechromosomefullyextendedifnotpackagedby

proteins?

Ans:1.6cm.InB-formDNA,thedistancebetweenadjacentnucleotidesis3.4A.Thuserefore,

thelengthofthechromosomewouldbe4.7x107x3.4A=16XM107A.andsincet_Thereare

108Apercm,sothelengthwouldbe1.6cm.

Page10

15.MeselsonandStahluseddensitylabelingofDNAtoshowthatDNAreplicationoccurs

W。3aasemiconservativemechanism.Intheirexperiment,theystartedwithanorganism

growninaheavydensitylabel(15N).Aftertwogenerationsofgrowthinlightmedium(the

morecommon14Nisotope),iftheDNAisisolatedandseparatedbydensity,howmany

bandswouldbeobservedandhowwouldtheirdensitycomparewiththestartingDNA?

Ans:In^eachgeneration,thenewlysynthesizedDNAiscomposedofoneparentalstrand

andonenewdaughterstrand.Aftertwogenerations,theDNAwouldyieldtwodifferent

densitybands^rtTwoofthedaughterswouldcontainoneoriginalheavyparentalstrandand

onelightdaughter(hybriddensity)strand,andtwoofthedaughterswouldcontaintwolight

strands(lightdensity).

Pages12,13

16.Thegeneticinformationoforganismsisalwaysintheformofnucleicacid.Give

examplesofcellularorganismsorothergeneticsystemswhosegenomesaredouble-

strandedDNA,single-strandedDNAZdouble-strandedRNA,orsingle-strandedRNA.

Ans:Livingorganisms(eitherprokaryoticoreukaryoticcells)alwayshavegenomesthatare

double-strandedDNA.However；4Thereare,however,manyvirusesofbothprokaryotesand

eukaryoteswhosegenomescanbesingle-strandedDNA,ordouble-orsingle-strandedRNA,

dependingonthevirus.

Page14

17.ThecentraldogmaofmolecularbiologyisthatgeneticinformationflowsfromDNAto

RNAbytranscription,andthentopolypeptidebytranslation.Giveanexampleofan

exceptiontothisgenerallytruestatement.

Ans:Retroviruseshavegenomesthataresingle-strandedRNA,andaspartoftheir

replicationcycletheyconverttheRNAintofirstasingle-strandedDNA(usinganenzyme

calledreversetranscriptase)andthenadouble-strandedDNA,inaprocesscalledreverse

transcription.Thedouble-strandedDNAcopyofitsgenomeintegratesintotheDNAofthe

hostcellitinfectsandfunctionsasanyothergene,directingthesynthesisofbothRNAand

polypeptide.Inthisexample,geneticinformationisflowingfromRNAtoDNA.

Page15

18.IstheenzymereversetranscriptaseanexampleofanRNApolymeraseoraDNA

polymerase?

Ans:ReversetranscriptasesareRNA-dependentDNApolymerasesthatuse

deoxynucleotidesassubstrates.

Page15

19.IntheprocessofDNAreplication,thetwoparentalstrandsseparateandserveas

templatesforthenewdaughterstrands.Duringthisprocess,arecovalentbondsbeing

broken?Explain.

Ans:No.Theseparationofthetwoparentalstrandsinvolvesbreakageofthehydrogen(H)

bonds(noncovalentbonds)betweenthecomplementarybasepairs.Thecovalent

phosphodiesterbondsbetweenadjacentnucleotidesoneachstrandarenotbroken.

Pages10,13,16

20.TheseparationofthedoublehelicalDNAincellsismediatedbyenzymescalled

helicases.Inthelaboratory,however,whatmethodiscommonlyusedtodenature(separate)

theindividualstrandsofadoublehelicalDNA?

Ans:DNAmaybedenaturedbyheatingtheDNAaboveitsTm,usuallybyboiling.

Page16

21.AscientistattheSanDiegoZooissentDNAsamplestoanalyze.Thesampleswere

collectedfromtwodifferentbacterialspeciesfromdifferentpartsoftheworld.She

determinesthattheG-Ccontentofoneofthemis32%andoftheotheris62%.Thelabels

havefallenoffthetubes,however,soshedoesnotknowwhichsamplewaiswhich.Oneof

theorganismsliveddeepintheoceanattemperaturesaround102Candtheotherwas

isolatedfromtheMojavedesert,wheretemperaturescanreachitcanbe459c.Which

sampleislikelytobewhich?

Ans:ThebacteriafromtheMojavedesertislikelytohaveaG-Ccontentof62%,whereasthe

oceanbacteriaislikelytohave型heG-Ccontentof32%.Thestabilityofthedouble-stranded

DNAisgreaterwithhigherG-CcontentbecauseG-CbasepairsaremorestablethanA-T

basepairs.Organismsthatthriveatelevatedtemperatureshavegenomeswithahigher

fractionofG-CbasepairstostabilizethedoublehelicalstructureoftheirDNA.

Page16

22.Onceamutationhasoccurredinagivengene,givethreetypesofeventsthatcanoccur

toreversetheeffectsoftheoriginalmutation.

Ans:1)Theremaybeatruereversionwherebytheoriginalbasechangeisreversed,orthe

insertionofgeneticmaterial,suchasatransposon,isdeleted.2)Theremaybeasecondsite

reversionwherebyasecondmutationinthesamegenechangestheaminoacidsequenceat

adistinctsitefromthefirstmutation7andallowsthepolypeptidetoregainfunction.3)

Theremaybeasuppressormutationinanothergene,alteringadifferentpolypeptide.This

changebypassestheneedfortheoriginalpolypeptideorenablesittointeractwiththe

mutantformoftheoriginalpolypeptide.

Page20

23.Whyisthemodifiedbase5-methylcytosineahot-spotformutations?

Ans:Theoxidativedeaminationof5-methylcytosineconvertsthisbasetothymine(noturacil1

asforordinarycytosine).TheDNArepairenzymeuracil-DNA-glycosidase,whichrecognizes

deoxyuracilasabnormalandremovesit,cannotdistinguishtheincorrectthyminefrom

othercorrectthymines,andthereforethenewT-Apairisnotrepaired.

Page21

24.OneofthemostcommoncausesofmutationsinDNAresultsfromtheoxidative

deaminationofcytosine.Whydoesthisleadtoamutation?

Ans:Duetooxidation,theaminogroupofcytosineisconvertedtoaketogroup,changing

thecytosinetouracil.Duringreplication,thenewuracilnowpairswithadenineinsteadof

thymine,resultinginaC-GpairbeingreplacedbyanT-ApairwhentheAnowpairswithTin

thenextreplicationcycle.

Page21

25.Notallinfectiousagentsthatcausediseasecontainnucleicacid.Whatistheinfectious

agentthatcausesscrapie,adiseaseofsheepandgoats?

Ans:Itisaprion--specifically,anabnormallyfoldedformofaproteincalledPrP.This

proteincanexistincellsinvariousconformations^andthosethatareresistantto

degradationbyproteasesnotonlycausedisease,but“convert“normallyfoldedPrPproteins

totheabnormalconformation.

Page23

Chap02,Chapter2

MultipleChoice

1.Achromosomeisbestdefinedas

A.thecompletesequenceofagene,includingsequencesremovedfromtheRNAproduct.

B.thefunctionalcodingsequencesofasingleDNAmolecule.

C.thecompletesetofhereditaryinformationofanorganism.

D.asinglelongmoleculeofDNA.

E.thesequenceofagenethathascodinginformationforthepolypeptideproduct.

Ans:D

Page28

2.Mutationisrandomwithrespecttothestructureandfunctionofagene.Asaresult,

A.theeffectsofaparticularmutationcannotbepredicted.

B.mutationsarelikelytoimpairthefunctionofagene.

C.mutationsareequallylikelyateverynucleotideofthegene.

D.mutationsinvariablydestroythefunctionofthegene.

E.mutationsarelikelytoimprovethefunctionofagene.

Ans:B

Page28

3.Inthecomplementationtest,crossingtwohomozygousrecessiveindividualswithsimilar

phenotypestoyieldallwild-typeoffspringmeansthat

A.thetwoparentscarrydifferentmutationsofthesamenucleotide.

B.thetwoparents'mutationsareInthesamegene.

C.thetwoparents'mutationsaffectdifferenttraits.

D.thetwoparentscarryidenticalmutations.

E.thetwoparents'mutationsareindifferentgenes.

Ans:E

Page29

4.Mutationsthathavenoapparenteffectarecalled

A.silentmutations.

B.loss-of-functionmutations.

C.nullmutations.

D.leakymutations.

E.gain-of-functionmutations.

Ans:A

Page30

5.Genesthatareonoppositeendsofalongeukaryoticchromosome

A.neverrecombine.

B.showlessthan50%recombination.

C.showexactly50%recombination.

D.showbetween50%and100%recombination.

E.show100%recombination.

Ans:C

Page34

6.Fullorpartialreversionofadeletionmutationmaybeaccomplishedby

A.aninsertionmutationinanothergene.

B.aninsertionmutationclosetotheoriginaldeletion.

C.asubstitutionmutationclosetotheoriginaldeletion.

D.aseconddeletionmutationclosetotheoriginaldeletion.

E.aseconddeletionmutationinanothergene.

Ans:B

Page35

7.Aclosedreadingframe

A.containsfrequentstopcodons.

B.containsmanysubstitutionmutations.

C.isformedbythedeletionofasequencefromanopenreadingframe.

D.beginsandendswiththesamesequence.

E.producesapolypeptidethatservesnoapparentfunction.

Ans:A

Page36

8.Thecolinearityofprokaryoticgenesmeansthat

A.withinaprokaryoticgene,bothDNAstrandsencodethesamepolypeptide.

B.aprokaryoticpolypeptidehasexactly3xasmanyaminoacidsasthenumberof

nucleotidesinthegeneencodingit.

C.prokaryoticproteinsareidenticalinlengthtotheirgenes.

D.prokaryoticgenescontainacontinuousunbrokensequenceencodingpolypeptide.

E.aphysicalmapofagenewillnotmatchtheaminoacidmapofitspolypeptideproduct.

Ans:D

Page37

9.TheproductionofRNAfromaDNAtemplateiscalled

A.splicing.

B.translation.

C.RNAprocessing.

D.transport.

E.transcription.

Ans:E

Page38,39

10.Aregulatorycontrolsiteofagene

A.mustbeveryclosetothegeneitaffects.

B.mustlieupstreamofthegeneitaffects.

C.isc/s-acting.

D.istrans-acting.

E.mustbeverydistantfromthegeneitaffects.

Ans:C

Page40

ShortAnswer

11.Whatisthedefinitionofageneticallele?

Ans:AgeneticalleleisanalternativesequenceofDNAforageneataspecificlocus.

Page27

12.Ifageneisduplicatedinthegenomesothatthetwocopiesresideatdifferent

chromosomallocations,arethesegenesalleles?

Ans:No.Allelesrefertoalternativeformsofageneataspecificlocusinthegenome,sothat

copiesevenofnearlyidenticalsequencesthatresideatdifferentlociarenotallelesofone

another(Insteadtheyarecalledparalogs).

Page27

13.Whyistheoriginalgeneticconceptofonegene:oneenzymenotentirelytrue?

Ans:AlthoughitistruethatgenesencodemRNAs,whichinturnencodepolypeptides,some

enzymesarecomposedofmorethanonepolypeptidechainandarethereforeencodedby

morethanonegene.Secondly,somegenescanproducealternativemRNAspecies(a

processtermedalternativesplicing)andthereforecangeneratemultiple(related)

polypeptides.

Page28

14.Howisgeneticcomplementationusedtodetermineiftwodifferentmutationsoccurin

thesamegeneordifferentgenes?

Ans:Ageneticcrossisperformedwithindividualsthateacharehomozygous(bothcopiesof

thegenehavethesamemutation)forthetwodifferentmutations.Ifthemutationsoccurin

thesamegene(butpossiblyatdifferentsiteswithinthegene),alloftheprogenywillexhibit

amutantphenotype,becausetheyhavenowild-typecopyofthegene.Ifthemutations

occurindifferentgenes,thentheprogenywillinheritonewild-typeallelefromeachparent

andwillbephenotypicallywild-type.

Page29

15.TherearemanytypesofchangesinDNAthatleadtomutations.Giveamolecular

explanationforthefollowingtypesofmutations:

A.anullmutation

B.aloss-of-functionmutation

C.again-of-fun