Molecular Biology Mcqs With Answer Explanation

Page1of5MolecularBiologyMCQswithanswerexplanation1.WhichofthefollowingistheprimarypurposeofusingaRNAisolationkit?A)ToisolategenomicDNAwithhighpurityB)ToextractandpurifytotalRNA,includingmRNA,rRNA,andtRNAC)ToamplifyRNAdirectlyfromacelllysateD)Toperformreal-timePCRwithoutRNAextractionAnswer:B)ToextractandpurifytotalRNA,includingmRNA,rRNA,andtRNAExplanation:QiagenRNAisolationkitsaredesignedtoextractandpurifytotalRNAfrombiologicalsamplesbyselectivelybindingRNAtoasilicamembrane,washingawaycontaminants,andelutingpureRNAfordownstreamapplicationssuchasRT-PCR.2.Inspincolumn-basedRNAextraction,whichreagentisresponsibleforlysingthecellsandinactivatingRNases?A)EthanolB)BufferRLTC)DNaseID)ProteinaseKAnswer:B)BufferRLTExplanation:BufferRLTcontainsguanidineisothiocyanate,whichlysescellsandinactivatesRNasestopreventRNAdegradationduringextraction.3.WhatisthefunctionofDNaseItreatmentduringRNAisolation?A)ToremovegenomicDNAcontaminationB)TodigestcellularproteinsC)ToenhanceRNAstabilityD)ToincreaseRNAyieldAnswer:A)ToremovegenomicDNAcontaminationExplanation:DNaseItreatmentisusedduringRNAisolationtodegradecontaminatinggenomicDNA,ensuringthattheRNAsampleisfreeofDNAbeforedownstreamapplicationslikeRT-PCR.4.Inreversetranscription-polymerasechainreaction(RT-PCR),whatistheroleofreversetranscriptase?A)ToamplifycDNAB)TosynthesizeRNAfromaDNAtemplateC)ToconvertRNAintosinglestrandedcomplementaryDNA(cDNA)D)ToconvertRNAintodoublestrandedcomplementaryDNA(cDNA)Answer:C)ToconvertRNAintosinglestrandedcomplementaryDNA(cDNA)5.WhichofthefollowingisNOTrequiredforcDNAsynthesisfromRNA?A)Oligo(dT)primersB)ReversetranscriptasePage2of5C)TaqpolymeraseD)dNTPsAnswer:C)TaqpolymeraseExplanation:TaqpolymeraseisathermostableDNApolymeraseusedinPCRamplificationbutisnotinvolvedincDNAsynthesis.Instead,reversetranscriptaseisusedtogeneratecDNAfromRNA.6Duringreal-timePCR(qPCR),whatistheprominentroleofSYBRGreendye?A)ItbindsspecificallytotargetsequencesB)Itfluorescesuponbindingtodouble-strandedDNAC)ItpreventsnonspecificamplificationD)ItinhibitspolymeraseactivityAnswer:B)Itfluorescesuponbindingtodouble-strandedDNAExplanation:SYBRGreenisafluorescentdyethatbindstodouble-strandedDNA,allowingreal-timequantificationofDNAamplificationinqPCR.7.WhatisthepurposeofahousekeepinggeneinRT-qPCRexperiments?A)ToserveasareferencefornormalizinggeneexpressiondataB)ToenhancePCRefficiencyC)ToimprovereversetranscriptionefficiencyD)ToactasatemplateforprimerdesignAnswer:A)ToserveasareferencefornormalizinggeneexpressiondataExplanation:HousekeepinggenesarestablyexpressedgenesusedasinternalcontrolstonormalizegeneexpressionlevelsinRT-qPCRexperiments.8.Inthecentraldogmaofmolecularbiology,whichenzymeisresponsiblefortranscription?A)DNApolymeraseB)RNApolymeraseC)ReversetranscriptaseD)LigaseAnswer:B)RNApolymeraseExplanation:RNApolymerasesynthesizesRNAfromaDNAtemplateduringtranscription.9.Whichofthefollowingbestdescribesthecentraldogmaofmolecularbiology?A)DNAProteinRNAB)RNADNAProteinC)DNARNAProteinD)ProteinRNADNAPage3of5Answer:C)DNARNAProteinExplanation:ThecentraldogmadescribestheflowofgeneticinformationfromDNAtoRNA(transcription)andfromRNAtoprotein(translation).10.InqPCR,whichdyebindstodouble-strandedDNAandfluoresces?A)SYBRGreenB)EthidiumbromideC)AlexaFluorD)HematoxylinAnswer:A)SYBRGreenExplanation:SYBRGreenbindstodouble-strandedDNAandemitsfluorescenceforreal-timequantification.11.WhatisthefirststepintheCentralDogma?A)DNAreplicationB)TranslationC)TranscriptionD)ReversetranscriptionAnswer:C)TranscriptionExplanation:TranscriptionistheprocessofcopyingDNAintoRNA.12.Whichenzymeisresponsiblefortranscription?A)DNApolymeraseB)RNApolymeraseC)ReversetranscriptaseD)HelicaseAnswer:B)RNApolymeraseExplanation:RNApolymerasesynthesizesRNAfromaDNAtemplate.13.WhatistheroleofethanolinRNAisolationusingQiagenkits?A)TolysecellsB)TobindRNAtothecolumnC)TodigestproteinsD)ToinhibitRNAdegradationPage4of5Answer:B)TobindRNAtothecolumnExplanation:EthanolhelpsRNAprecipitateandfacilitatesitsbindingtothesilicamembraneinthespincolumn.14.Whatistheroleofribosomesingeneexpression?A)DNAreplicationB)mRNAsynthesisC)ProteinsynthesisD)RNAdegradationAnswer:C)ProteinsynthesisExplanation:RibosomestranslatemRNAintoproteins.15.WhatisthepurposeofaninternalcontrolinRT-qPCR?A)TocheckforgenomicDNAcontaminationB)ToconfirmprimerspecificityC)TovalidateRNAqualityandnormalizeexpressiondataD)ToincreasecDNAyieldAnswer:C)TovalidateRNAqualityandnormalizeexpressiondataExplanation:Internalcontrolshelpensureaccuratequantificationofgeneexpression.16.WhichRNAmoleculeisusedasatemplateforreversetranscription?A)rRNAB)tRNAC)mRNAD)siRNAAnswer:C)mRNAExplanation:mRNAservesasthetemplateforcDNAsynthesis.17.WhyisMgrequiredinPCRreactions?A)ItstabilizesDNAB)ItactivatesTaqpolymeraseC)ItbindstoprimersD)ItinhibitsRNAdegradationAnswer:B)ItactivatesTaqpolymeraseExplanation:MagnesiumionsareessentialcofactorsforTaqpolymeraseactivity.18.InqPCR,whatisaCtvalue?A)ThemeltingtemperatureofDNAB)ThecyclenumberatwhichfluorescencereachesthethresholdC)ThefinalconcentrationofDNAD)ThedenaturationsteptemperaturePage5of5Answer:B)ThecyclenumberatwhichfluorescencereachesthethresholdExplanation:TheCtvalueindicatesthecycleatwhichamplifiedDNAisdetected.19.WhatisthefunctionofRibonuclease(RNase)?A)TodegradeDNAB)TosynthesizeRNAC)TodegradeRNAD)ToamplifyRNAAnswer:C)TodegradeRNAExplanation:RNasesbreakdownRNAmolecules.20.InDNAisolation,whyisisopropanolused?A)TodissolveDNAB)ToprecipitateDNAC)TodegradeproteinsD)TolysecellsAnswer:B)ToprecipitateDNAExplanation:IsopropanolhelpsconcentrateandprecipitateDNAfromsolution.