山东大学分子生物学习题.docx

山东大学分子生物学习题.docx

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山东大学分子生物学习题

ChapterExercise

（1）TheMendelianViewoftheWorld

1Acombinationofclevernessand,perhaps,luckledMendeltousethegardenpeaforhisseriesofexperiments.Describethecharacteristicsofthisorganismthatmadeitanidealchoiceforhisstudies.

2Explainwhetheramammal（forexample,thehuman）wouldbesuitableforasimilarstudyininheritance.

3DefineMendel'stwolaws.Explainwhattheymeanatthelevelofhowchromosomesbehavefollowingfertilization,andduringmeiosis.Dobothlawsalwaysapply?

4Whatdoesitmeanwhenanorganismissaidto"breedtrue"foratrait?

Whatdoesthismeanintermsoftheorganism'sgenotype?

5ProvideanexampleofatraitthatdoesnotbehaveaccordingtotheclassicalMendeliandominant-recessiverelationship.Speculateastowhattypesofalleleswouldinteractinatruedominantandrecessivefashion,andwhichmightshowamoreintermediateinteraction.

6Designacrossthatwouldallowyoutodistinguishbetweentwoplantsshowingadominantphenotype,butcouldbeeitherhomozygousorheterozygousforthedominantallele.

7Inanunusualrodent,coatcolormaybeeitherredorbrown.Tworedfemalesarecrossedindependentlywiththesamebrownmale.Inseverallittersresultingfromthecrosswiththemale,female#1produced19redoffspring.Inseverallittersresultingfromthecrosswiththemale,female#2produced11redoffspringand9brown.Describethepatternofinheritanceofcoatcolorinthisanimal,andsuggestthegenotypeofeachoftheparents.

8Howmanygeneticallydistinctgametescanbeformedforeachorganismhavingthefollowingdiploidcontent:

1AaBbCcDd

1AaBbccDd

1AABBCcdd

1AabbCCDD

9Foreachcaseinquestion8（a--d）,listthepossibilities.

10GenesW,Y,Zassortindependentlyandaredominantovertheircorrespondingallelesw,y,z.Setupacrossbetweentwoindividualsheterozygousforeachtrait[WwYyZzxWwYyZz].

1Whatisthefrequencyofoffspringresultingfromthecrosswhoarehomozygous---thatis,whosegenotypeis[WWYYZZ]?

1Whatisthefrequencyofoffspringwhosephenotypeisdominantforallthreetraits?

11Whatpropertiesofchromosomessuggestedtoearlygeneticiststhattheymightharborthegeneticmaterial?

Whatexperimentsconfirmedthesesuspicions?

12Describethechromosomaleventsthatunderliegeneticrecombination.Inwhatcelltypesdoesrecombinationoccur?

Drawacrossing-overeventinacell,andshowthegametesthatwouldbeproducedbytheevent

13Ifageneatoneendofachromosomehasarecombinationfrequencyof50%withagenelocatedatthecenterofthechromosome,andthecentrally-locatedgenehasanequivalentfrequencyofrecombinationwithathirdgenepresentattheoppositeendofthechromosome,whatistherecombinationfrequencybetweenthetwoterminalgenes?

Whatcanwesayaboutthenumberofmapunitsseparatingeachofthesethreegenes?

14Youdeterminethefrequencyofrecombinationbetweentwogenestobe50%.Whatcanyouconcludeabouttherelativechromosomalpositionsofthetwogeneswithinthegenome?

Whatotherinformationorexperimentalresultsmighthelpyoudeterminewhetherthegenesareonthesamechromosomeorondifferentchromosomes?

15Youarecharacterizingtwogenespresentonasingleplantchromosome,andwouldliketodeterminetherecombinationfrequencybetweenthem.Designanexperimentalstrategyfordoingthis.Assumethateachofthegenesincludesadominantandrecessiveallele.Describethegenotypesoftheplantsyouwouldneedtocross,andexplainhowyouwoulddeterminetherateofrecombination.

16InachromosomehavingthegeneorderA-B-C,ifthefrequencyofrecombinationbetweenmarkersaandbis0.15,andthefrequencybetweenmarkersbandcis0.07,whatistherateofrecombinationbetweenmarkersaandc?

Whyisitnotpossibletosimplyaddthesetwofrequenciestogethertoobtaintherecombinationfrequencyfortheoutermarkers?

17Acrossinvolvingthreegenesonasinglechromosomegivesthefollowingfrequencyofrecombinantprogeny:

ABBCAC

25%17%12%

Whatistheorderofthesethreegenesonthischromosome?

Whatothercrosscouldyouperformtoconfirmyourconclusion?

18ThedevelopmentofMendeliangeneticswasaccompaniedbydoubtaboutwhetherthetypesofgeneticalterationsobservedinthelabcouldadequatelyexplainthemajorstructuralleapsseenduringevolution.Whattypeofgeneticanalysisputthesedoubtstorest,andwhattypesofconclusionsdidtheyreachinordertodoit?

19FollowingtherediscoveryofMendel'slaws,researchersbegantheirsearchforthechemicalnatureofthegeneticmaterialinearnest.Theirsearchreliedonanumberoffunctionalandphysicalpropertiesthattheyknewthegeneticmaterialmustpossess.Nameatleastthreeoftheseproperties.

20Oneoftheearliesthumantraitstobesuccessfullydissectedatthemolecularlevelwasphenylketonuria,ametabolicdisorderinvolvingadefectinaminoacidmetabolism.Howdoesthismetabolicdefectleadtoadiseasephenotype?

Whyweremetabolicdisorderssuchasthisparticularlyusefulforearlystudiesintotherelationshipbetweengenesandproteins?

（2）NucleicAcidsConveyGeneticInformation

1InGriffith'sexperimentswithvirulenceinbacteria,howdidhedemonstratethatthetransformationfromnonvirulencetovirulencewastrulyahereditarychange?

Intheabsenceofsuchademonstration,whatotherexplanationscouldhaveaccountedforhisresults?

2HowdidtheexperimentalapproachesofAvery,MacLeod,andMcCartyvs.thoseofHersheyandChasedifferindemonstratingthenatureofgeneticmaterial?

3Priondiseasesareagroupofneurodegenerativediseasesthatappeartobeentirelytransmittedbyproteins,withnoessentialrolefornucleicacids.KeepinginmindtheexperimentsofAveryetal.,howdoyouthinktheabsenceofarolefornucleicacidsinprioninfectivitywasexperimentallyestablished?

4DescribeChargaff'sexperimentsaddressingthenucleotidecompositionofDNA.WhatdidhisresultssayaboutthestructureofDNAandabouthowDNAstoresinformation?

5HowdidX-raydiffractionstudiescontributetothediscoveryofthestructureofDNA?

Whatspecificinsightswereprovidedbythesestudies?

6ExplainhowthedesignoftheMeselsonandStahlexperimentsaddressedthequestionofDNAreplication.

7DrawthereactioncatalyzedbyDNApolymerase.WhatdeterminesthesequenceoftheDNAproducedbythereaction?

Describetheexperimentsthatwerecarriedouttodemonstratethis.

8OnwhatbasisdidresearchersreasonthatDNAwasmostlikelynotthetemplateforproteinsynthesis?

WhatevidenceledtotheconclusionthattherealtemplatewasRNA?

9Describethreemajordifferencesbetweenthestructuresofdeoxyribonucleicacidsandribonucleicacids.

10Whatisthe"centraldogma"concerningtheflowofgeneticinformation?

Isitalwaysvalid?

11WhatreasoningledFrancisCricktoproposethatanadaptormoleculeintervenesbetweenmessengerRNAandaminoacids?

Whatdidtheadaptorturnouttobe?

12（a）YouwouldliketoisolaterRNA,tRNA,andmRNAfromaparticularcelltype.WhatpropertiescanyourelyontodistinguishbetweenthesethreetypesofRNA---forexample,intermsoftheirsize,complexity,GCcontent,orabundanceinthecell?

（b）rRNAandmRNAbothinteractwithribosomes,butinfundamentallydifferentways.DescribethedifferencesinthewayeachofthesetwotypesofRNAinteractswithribosomes.

13Whatistheadvantageofhavingeachaminoacidspecifiedbyasequenceofthreenucleotides?

Whywouldtwohavebeentoofew?

Canyouthinkofanyreasonswhyfourwouldbedisadvantageous?

14Indetermininghowmanybasesarerequiredtospecifyanaminoacid（thatishowmanybasesconstituteacodon）,FrancisCrick,SydneyBrenner,andcolleaguesusedaclassofmutagensthatcauseinsertionsanddeletionsofsinglebasepairsinDNA.IngeneX,predictthephenotypeofmutantshaving,respectively,onethroughsixinsertionmutations,andexplainhowtheseresultsmightbeusedtodeterminethecodingpropertiesofDNA.

A

+

?

B

++

?

C

+++

?

D

++++

?

E

+++++

?

F

++++++

?

15Onceithadbeenestablishedthatcodonsconsistofsetsofthreenucleotides,whatapproachdidNirenbergandMatthaeiusetobegincrackingthecode?

Whatwasthefirstcodonthattheydeciphered?

（3）TheImportanceofWeakChemicalInteractions

1Youpurifyanenzymeandwouldliketodeterminewhetheritiscomposedofasinglepolypeptidechainormultiplechainsheldtogetherbysecondarybonds.Howmightyougoaboutdistinguishingbetweenthesepossibilities?

2Listthreegeometricfeaturesdistinguishingatomsconnectedbyacovalentbondversusthoseconnectedbyaweakbond.Howmightthesedifferencescomeintoplaywhentwomacromoleculesinteract?

3DescribehowstrongandweakbondsareinvolvedintheprocessofDNAreplication,addressingtheroleofatleasttwoexamplesofeachtypeofbond.

4Whichismorelikelytoinvolvethemostsignificantlossoffreeenergy:

thehybridizationoftwo100basepairstretchesofsingle-strandedDNAtoformadoublehelix,anenzymebindingtoitssubstrate,oranantibodybindingtoanantigen?

Explainyouranswer.

5Whathappenstotheleveloffreeenergyduringaspontaneousreaction?

Whenfreeenergyislostduringareaction,whatbecomesoftheenergy?

Whatoccurswhenacollectionofatomsreachesitslowestenergystate?

6The（Gassociatedwithaproteinbindingtoanidenticalproteintoformahomodimeris--2kcal/mol.WhatistheKeqofthisinteractionat25°C?

Whatdoesthissayaboutthebindingoftheseproteinsatthistemperature?

7Describeandcompareth