Download PGI PG 2020 May Biochem Solved Question Paper

Download PGIMER (Post Graduate Institute of Medical Education & Research, Chandigarh) 2020 May Biochem Solved Question Paper

1.WhichofthefollowingarePyrimidinebases?
a)AdenineandGuanine
b)GuanineandCytosine
c)CytosineandAdenine
d)ThymineandCytosine
e)None
CorrectAnswer-D
Ans:(D)CytosineandAdenine
InDNAandRNA,Pyrimidinebasesformhydrogenbondswiththeir
complementarypurines.
Thus,inDNA,thepurinesadenine(A)andguanine(G)pairup
withthepyrimidinesthymine(T)andcytosine(C),respectively.
InRNA,thecomplementofadenine(A)isuracil(U)insteadof
thymine(T),sothepairsthatformareadenine:uraciland
guanine:cytosine.
Twotypesofbasesarefoundinnucleotides:(i)purinesand(ii)
pyrimidines.
1. Purines:TwomajorpurinebasesfoundbothinDNAsaswellas
RNAsare(i)adenine(A)and(ii)guanine(G).
2. Pyrimidines:Threemajorpyrimidinebasesare(i)cytosine(C),(ii)
Uracil(U)and(iii)Thymine(T).Cytosineanduracilarefoundin
RNAsandcytosineandthyminearefoundinDNAs.Uracilisnot
foundinDNAsQandthymineisnotfoundinRNAs.
Ref:RodwellV.W.(2011).Chapter32.Nucleotides.InD.A.Bender,
K.M.Botham,P.A.Weil,P.J.Kennelly,R.K.Murray,V.W.Rodwell
(Eds),Harper'sIllustratedBiochemistry,29e

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2.Majorcontributiontowards
gluconeogenesisisby?
a)Lactate
b)Glyerol
c)Ketones
d)Alanine
e)None
CorrectAnswer-D
Di.e.Alanine

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3.Whichofthefollowingisnotapyrimidine
base?
a)Cytosine
b)Uracil
c)Guanine
d)Thymine
e)Adenine
CorrectAnswer-C
Ans.is'c'i.e.,Guanine
PurinesPyrimidines
AdenineCytosine
GuanineUraciI
Thymine
Bothpurines(adenineandguanine)arefoundbothinDNA&RNA.
Amongpyrimidines-
LiCytosineanduracilarefoundinRNA(thymineisnotfoundin
RNA).
CytosineandthyminearefoundinDNA(uracilisnotfoundinDNA).
InDNA,adenineisalwayspairedwiththyminebytwohydrogen
bonds;andguaninealwayspairedwithcytosinebythreehydrogen
bonds.

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4.Glycogenstoragedisorderis-
a)Niemann?Pickdisease
b)Gaucherdisease
c)Tay-Sacksdisease
d)Pompe'sdisease
e)McArdlesdisease
CorrectAnswer-D
GlycogenstoragediseasetypeII,alsocalledPompedisease,is
anautosomalrecessivemetabolicdisorder[1]whichdamages
muscleandnervecellsthroughoutthebody.Itiscausedbyan
accumulationofglycogeninthelysosomeduetodeficiencyofthe
lysosomalacidalpha-glucosidaseenzyme.Itistheonlyglycogen
storagediseasewithadefectinlysosomalmetabolism,andthefirst
glycogenstoragediseasetobeidentified,
Thediseaseiscausedbyamutationinagene(acidalpha-
glucosidase:alsoknownasacidmaltase)onlongarm
ofchromosome17.
Mostcasesappeartobeduetothreemutations.Atransversion(T
G)mutationisthemostcommonamongadultswiththisdisorder.
ThismutationinterruptsasiteofRNAsplicing.
Thegeneencodesaprotein--acidalpha-glucosidase(EC3.2.1.20)
--whichisalysosomalhydrolase.Theproteinisanenzymethat
normallydegradesthealpha-1,4andalpha-1,6linkages
inglycogen,maltoseandisomaltoseandisrequiredforthe
degradationof1?3%ofcellularglycogen.Thedeficiencyofthis
enzymeresultsintheaccumulationofstructurallynormalglycogen
inlysosomesandcytoplasminaffectedindividuals.

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clinicalfeatures:
Accumulationofglycogeninlysosomes:Juvenileonsetvariant,
musclehypotonia,deathfromheartfailurebyage2;adultonset
variant,muscledystrophy

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5.Whichofthefollowingwillbemore
towardsthenegativepoleingel
electrophoresis?
a)5bp
b)50kbp
c)150bp
d)550bp
e)50000bp
CorrectAnswer-B:E
Ans.is'b'i.e.,50kbp&'e'i.e.50000bp[RefVariousinternet
sites]
Ingelelectrophoresis,DNAmoleculesmovetowardspositiveendas
theyarenegativelychargedthemselves.
largermolecules(>500bp)moveslowlyascomparedtosmaller
molecules.So,largerthemolecule,itismoretowardsthenegative
endandviseverse.
Polyacrylamidegelsareusuallyusedforproteins,andhavevery
highresolvingpowerforsmallfragmentsofDNA(5-500bp).
Agarosegelsontheotherhandhavelowerresolvingpowerfor
DNAbuthavegreaterrangeofseparation,andarethereforeused
forDNAfragmentsofusually50-20,000bpinsize,butresolutionof
over6Mbispossiblewithpulsedfieldgelelectrophoresis(PFGE)"-
wikipedia

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6.Betagalactosidasedeficiencycauses?
a)Goucherdisease
b)Krabbe'sdisease
c)Fabry'sdisease
d)NeimannPickdisease
e)Metachromaticleukodystrophy
CorrectAnswer-B
Ans.is'b'i.e.,Krabbe'sdisease[RefHarper30th/ep.251&
29thiep.235]
Krabbedisease,alsoknownasgloboidcellleukodystrophyor
galactosylceramidelipidosis,isanautosomal-recessive
sphingolipidosiscausedbydeficientactivityofthelysosomal
hydrolasegalactosylceramidebeta-galactosidase(GALC).
GALCdegradesgalactosylceramide,amajorcomponentofmyelin,
andotherterminalbeta-galactose-containingsphingolipids,including
psychosine(galactosylsphingosine).
Beta-galactosidaseisalysosomalenzymeresponsibleforcatalyzing
thehydrolysisofgangliosides.Thedeficiencyofthisenzymecan
leadto1ofthefollowingconditions:GM1gangliosidosis,Morquio
syndromeB,andgalactosialidosis.

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7.Trueregardingphenylketoneureais?
a)Mustyorderisduetophenylalanineinsweat
b)Deficientenzymeisphenylalaninehydroxylase
c)Autosomaldominant
d)Maybeassociatedwithimpairedmentaldevelopment
e)Infantsarenormalatbirth
CorrectAnswer-B:D:E
Ans.is'b'i.e.,Deficientenzymeisphenylalanine
hydroxylase,'d'i.e.Maybeassociatedwithimpairedmental
development&'e'i.e.Infantsarenormalatbirth
[RefHarper's30th/ep.304&29m/ep.288;Chatterjee5th/ep.426]
InPhenylketonuriathereisinabilityofoxidationofphenylalanineinto
tyrosine.Thereisdefectivefunctionofphenylalaninehydroxylase.
Toxiclevelsofphenylalanine(andinsufficientlevelsoftyrosine)can
interferewithinfantdevelopmentinwayswhichhavepermanent
effects.
Thediseasemaypresentclinicallywithseizures,hypopigmentation
anda"mustyodor"tothebaby'ssweatandurine(dueto
phenylacetate,acarboxylicacidproducedbytheoxidationof
phenylketone).
Untreatedchildrendevelopmicrocephaly,anddemonstrate
progressiveimpairmentofcerebralfunctionwhichcanleadto
intellectualdisability,behavioralproblems,andmentaldisorders.

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8.Methodsthatcanbeusedtoseeprotein-
proteininteractioninclude?
a)Fluorescencelifeimaging
b)Fluorescenceresonanceenergytransfer
c)Fluorescencepolarization
d)Fluorescencecomplementation
e)Alloftheabove
CorrectAnswer-E
Ans.is'e'i.e.,Alloftheabove[Refwiki]
Biochemicalmethods
1. Co-immunoprecipitation
2. Bimolecularfluorescencecomplementation(BiFC)
Biophysical&theoreticalmethods
1. Bio-layerinterferometry
2. Dualpolarisationinterferometry(DPI)
3. Fluorescencepolarization/anisotropy
4. Fluorescenceresonanceenergytransfer(FRET)
5. Fluorescencelifetimeimagingmicroscopy(FLIM).

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9.Uncouplersofoxidativephosphorelation
include?
a)2,4-DNP
b)H2S
c)Cyanide
d)Thermogenin
e)Carboxin
CorrectAnswer-A:D
Ans.is'a'i.e.,2,4-DNP&'d'i.e.,Thermogenin[RefHarper
30thiep.132er29thlep.339;Vasudevan6thIep.234,235;
ChatterjeaShinde7th/ep.132;LippincottOlep.79]
Uncouplersblockthecouplingofoxidationwithphosphorylation.
Thesecompoundsallowthetransferofreducingequivalentsin
respiratorychainbutpreventthephosphorylationofADPtoATPby
uncouplingthelinkagebetweenETCandphosphorylation.
Uncouplersmaybe:?
1. Natural:-Thermogenin,thyroxine,longchainFAs
2. Synthetic:-2,4-dinitrophenol(2,4-DNP),2,4-dinitrocresol(2,4-
DNC),andCCCP.
Thermogeninisanuncouplerproteinpresentinmitochondriaof
brownadiposetissue(brownfat).
Ituncouplesoxidationandphosphorylationbyactingasachannel
forH+ionssothathydrogeniongradientcannotbuildup

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10.Pyridoxineisrequiredfor?
a)Decarboxylation
b)Carboxylation
c)Transamination
d)Transsulfuration
e)Oxidativedeamination
CorrectAnswer-A:C:D
Ans.is'a'i.e.,Decarboxylation,'c'i.e.Transamination&'d'i.e.
Transsulfuration[RefHarper's30m/ep.557&29th/ep.536,
537]
1. Transamination:PLPactsascoenzymefortransaminases.
2. Decarboxylation:Alldecarboxylationreactions(bydecarboxylases)
requirePLP.ThusPLPisinvolvedingenerationofimportant
biogenicamines:GABA,Serotonin,Melatonin,Histamineand
catecholamines(epinephrine,norepinephrine).
Inpyridoxindeficiency,3-hydroxykinurenineaccumulatesandis
convertedtoalternatemetabolitexanthurenicacid(xanthurenate).
Thus,xanthurenicacid(xanthurenate)excretioninurineisincreased
inpyridoxinedeficiency.Thuspyridoxinmaybeusedinxanturenic
aciduria.

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11.Aminoacidsderivedfromtissuesare
directedtowards?
a)Ammoniaformation
b)Ammoniumsalts
c)Ureacycle
d)Ureaformation
e)Aminoacidpoolofcells
CorrectAnswer-E
Ans.is'e'i.e.,Aminoacidpoolofcells[Ref:Harper30"/ep.
298;NutritionbyPaulInsel,DonRoss,KimberleyMc?Mahon
4th/ep.242]
Whencellsbreakprotein,theprotein'saminoacidsreturnto
circulation.Theseavailableaminoacids,foundthroughoutthebody
tissuesandfluids,arecollectivelyreferredtoasaminoacidpool.
Theavailableaminoacidswillbeutilizedforproteinsynthesis.
Othersmayhavetheiraminogroupremovedandbeusedto
produceenergyornonproteinsubstancessuchasglucose.

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12.Co-factorsrequiredforfattyacid
synthesisinhumanare?
a)ATP
b)NADPH
c)Biotin
d)Pyridoxine
e)Pentothenicacid
CorrectAnswer-A:B:C
Ans.is'a'i.e.,ATP,'b'i.e.NADPH&'c'i.e.,Biotin[RefHarper
30thlep.236er29th/ep.219;Lippincott4'5/ep.187]
pyridoxalphosphateisneededforelongationofalreadysynthesized
fattyacids,notforsynthesisitself.
Extramitochondrial(cytoplasmic)Systemisconcernedwithdenovo
synthesisoffattyacidfromacetylCoA,andispresentincytosaol.
Palmiticacidissynthesized.
CofactorrequirementsforfattyacidsynthesisareNADPH,ATP,
Mn+2,biotinandHCO3-(asasourceofCO2).
Themajorproductoffattyacidssynthesisispalmitate.Longerfatty
acidsareformedbyelongationreactionseitherinmicrosomes
(endoplasmicreticulumorinmitochondria.

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13.AllareTruestatementsregardingOkazaki
fragmentEXCEPT?
a)RequiresDNApolymerase
b)Formsonleadingstrand
c)Formsonlaggingstrand
d)Requireshelicaseforopening
e)RequiresRNAprimer
CorrectAnswer-B
Ans.is'b'i.e.,Formsonleadingstrand[RefLippincott's5thiep.
399,401,406;Harper's30lep.383&250/ep.367]
DNApolymerasesresponsibleforcopyingtheDNAtemplatesare
onlyableto"read"theparentalnucleotidesequencein3'-5'
direction,andtheysynthesizethenewDNAstrandsonlyin5'-3'
direction.Therefore,2newlysynthesizedchainsmustgrowin
oppositedirections.
TheDNAchainwhichrunsinthe3'to5'directiontowardsreplication
forkascontinuedstrandiscalledleadingstrand.Thisrequiresonly
oneRNAprimer
TheDNAchainwhichrunsinthe5'to3'directionawayfromthe
replicationforkiscalledlaggingstrand.Itissynthesized
discontinuouslyandrequiresnumerousRNAprimers.
Asthereplicationforkmoves,RNAprimersaresynthesizedat
specificintervals.TheseRNAprimersareextendedbyDNA
polymeraseIIIintoshortpiecesofDNAcalledOkazaki
fragments.

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14.AllaretrueregardingsatelliteDNA
EXCEPT?
a)RepeatedDNAsequencesintandem
b)Clusteredaroundcentromere
c)Clusteredaroundtelomeres
d)Transcriptionallyactive
e)Noneoftheabove
CorrectAnswer-D
Ans.is'd'i.e.,Transcriptionallyactive[RefHarper's30"'/ep.
377-78;Lippincot4t5lep.461]
RepetitivesequencesinDNAisalsocalled(satelliteDNA)
Theseconsistof5-500basepairlengthsrepeatedmanytimes.
Theseareoftenclusteredincentromeres(centralproteinof
chromosomeswheresisterchromatidsjoineachother)and
telomeres(repeatedsequenceattheendofchromosomes).
Themajorityofthesesequencesaretranscriptionally
inactiveandplayastructuralrole
microsatellitesequencesmostcommonlyarefoundasdinucleotide
repeatsofACononestrandandTGontheoppositestrand.
Microsatelliterepeatsequencesconsistof2-6bprepeatedupto50
times.TheACrepeatsequencesoccurat50000-100000locationsin
humangenome.

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15.Truestatementregardingt-RNAis?
a)Containscodon
b)Containsanti-codon
c)Containsbluntends
d)Actsasaacceptorforaminoacidsinproteinsynthesis
e)Getsattachedtoribosomes
CorrectAnswer-B:D:E
Ans.is'b'i.e.,Containsanti-codon,'d'i.e.Actsasaacceptor
foraminoacidsinproteinsynthesis&'e'i.e.Getsattachedto
ribosomes
[RepLippincoteselep.418;Harper's30'Vep.394]
tRNAistheSmallestofthethreemajorRNAShaving73to93
nucleotideresidues.Itcomprisesabout15%oftotalRNAinthecell.
Acceptorarmconsistsofabasepairedstemthatterminatesin
thesequenceCCAatthe3'end.Thisistheattachmentsitefor
aminoacids.CCAtailisaddedduringpost-transcriptional
modification.
Itcontainsanticodonthatbasepairswiththecodonofcoming
mRNA.Anticodonhasnucleotidesequencecomplementarytothe
codonofmRNAandisresponsibleforthespecificityofthetRNA.
ThroughTCarmtRNAgetsattachedtoribosome.

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16.Examplesofchaperonincludeallexcept?
a)Calreticulin
b)Calnexin
c)Calbindin
d)BiP
e)Ubiquitin
CorrectAnswer-C:E
Ans.is'c'i.e.,Calbindin&`e'i.e.Ubiquitin[RefHarper's30th/e
p.609;Vasudevan5thlep.17]
Chaperonesarepresentinawiderangeofspeciesfrombacteriato
humans.Manysocalled'Heatshockproteins'(HSP)are
chaperones.Theyarealsoknown/asstressproteins.
SomeChaperonesandEnzymesInvolvedinFoldingthatare
LocatedintheRoughEndoplasmicReticulumareBiP
(immunoglobulinheavychainbindingprotein),GRP94(glucose-
regulatedprotein),GRP-170,GRP-78,Calnexin,CalreticulinPDI
(proteindisulfideisomerase),PPI(peptidylprolylcis-trans
isomerase),HSP47,ERp29

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17.VitaminEdeficiencyinadultcauses?
a)Hemolysis
b)PosteriorcolumnInvolvement
c)Peripheralneuropathy
d)Hairloss
e)Impairedimmunity
CorrectAnswer-A:B:C:D:E
Ans.is'All'i.e.,a,b,c,d&e[Ref:Harper's30th/ep.553&29th/e
p.532,541,543]
vitaminEdeficiencyarecharacterizedbyaxonaldegenerationinthe
posteriorcolumnsandaselectivelossoflargecalibremyelinated
sensoryaxonsinthespinalcordandperipheralnerves.
Subacutecombineddegenerationofspinalcord,alsoknownas
Lichtheim'sdisease,referstodegenerationoftheposteriorand
lateralcolumnsofthespinalcordasaresultofvitaminB12
deficiency(mostcommon),vitaminEdeficiency,andcopper
deficiency.
VitaminEactiviyispresentinseveraltocopherols,themost
importantbeinga-,y-and8-tocopherol.a-Tocopherolisthemost
abundantandistakenasthestandard.
SeleniumandvitaminEsupplementeachotherbytheiranti-oxidant
property.
Hemolyticanemia-duetooxidativedamagetoredblood
cells,Impairmentoftheimmuneresponse,Digestiveproblems&
Malabsorptionleadingtoliverandpancreaticproblems,Dryskin
andhairloss

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18.VitaminCdeficiencyisassociatedwith?
a)Decreasedimmunity
b)Improperwoundhealing
c)Epistaxis
d)Seizures
e)Anemia
CorrectAnswer-A:B:C:E
Ans.is'a'i.e.,Decreasedimmunity,'b'i.e.,Improperwound
healing,'c'i.e.,Epistaxis&`e'i.e.,Anemia[RefHarper's30thle
p.561-65;Internet]
GeneralsymptomsincludeLowgradefever,irritability,tachypnea,
digestivedisturbances,lossofappetite,weakness,weightloss,
vaguemyalgiasandarthritis&arthralgias.
AnemiaDuetodefectinutilizationofiron&folicacid.
Dermatological:-Dryskin,Follicularhyperkeratosis,coiledhair,
splittingofhair,Poorwoundhealing
Impairedimmunityleadingrecurrentinfections,Irritabilityandother
psychologicsymptoms.

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19.Trueabouttelomeraseis?
a)DNAdependentRNApolymerase
b)RNAdependentDNApolymerase
c)Reversetranscriptaseenzyme
d)Increasedtelomeraseactivityisseeninsomaticcells
e)Telomeraseincreasesthelongevityofcells
CorrectAnswer-B:C:E
Ans.is'b'i.e.,RNAdependentDNApolymerase,'c'i.e.Reverse
transcriptaseenzyme&`e'i.e.Telomeraseincreasesthe
longevityofcells[RefHarper29th/ep.358&28`"/ep.315,316;
Robbin's8th/ep.40,296]
Telomeraseisareversetranscriptase(RNAdependentDNA
polymerase)andisresponsiblefortelomeresynthesisand
maintainingthelengthoftelomers(replicationofendof
chromosome).Thus,telomeraseprovidelongevitytothecellswhich
containthisenzyme.
Telomeraseisabsentfrommostofthesomaticcellsandhencethey
sufferprogressivelossoftelomeresandtheyexitthecellcycle.
Senscentcellslacktelomerasesotheirtelomeresgetshortenedby
criticallengthandthesecellsremainsinGophase

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20.Whichis/arenottransportprotein?
a)Transferrin
b)Collagen
c)Ceruloplasmin
d)Hemoglobin
e)Albumin
CorrectAnswer-B
Ans.is'b'i.e.,Collagen[Ref
http://www.gastrohep.com/ebooks/rodes/Rodes_2_4_1.pdf]
Collagenisastructuralprotein
Albuminhascirculatingtransportproteinssuchassteroids,
thyroxine,triiodothyronine,fatsolublehormones,fattyacidstoliver,
unconjugatedbilirubin,manydrugs,Calcium,magnesium,cations&
anions.
CeruloplasminhasCopper
HemoglobinOxygenfromlungtotisuues
Transferrinironionsintheferricform(Fe3+).

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21.FullformofLCATis?
a)Lecithincholesterolacyltransferase
b)Lecithincholesterolalkyltransferase
c)Lecithincholineacetyltransferase
d)Lecithincholinealcoholtransferase
e)LecithincoAtransferase
CorrectAnswer-A
Ans.is'a'i.e.,Lecithincholesterolacyltransferase[Ref
Harper's30`Vep.272;Lippincott6thlep.234]
Lecithin-cholesterolacyltransferase(LCAT)ispresentinHDLand
esterifiesthecholesterolinHDL.MajoractivatorofLCATisApo-Al.
Apo-C1canalsoactivateLCAT.
HDL-Cholesterolappearstobethebestindependentpredictorof
coronaryarterydisease(inverserelationship)thananyotherknown
riskfactor.ThatmeanslowHDLisamuchstrongerpredictorof
coronaryarterydiseasethanincreasedLDLcholesterolorincreased
totalcholesterol
Theintracellularcholesterolactivatestheintracellularenzymeacyl-
CoAcholesterolacyltransferase(ACAT).Thisenzymecatalyzes
transferofanacylgroupfromafattyacidderivativetocholesterol,
resultingintheformationofesterifiedcholeserol,andthischolesterol
esterisstoredforsubsequentuse.

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22.Whichorgancannotuseketonebodies?
a)Brain
b)RBC
c)Muscle
d)Heart
e)Liver
CorrectAnswer-B:E
Ans.is'b'i.e.,RBC&`e'i.e.,Liver[RefHarper's30th/ep.227;
Vasudevanelep.145]
LiveritselfcannotutilizeketonebodiesasitlackstheenzymeCoA-
transferasewhichisrequiredforactivationofketonebody.
Besideliver,RBCsalsodonotutilizeketonebodies(onlyglucoseis
thesolefuelforRBCs).
Acetoacetateandp-hydroxybutyrateareusedinpreferenceto
glucoseasenergysourcebycertaintissues,e.g.heart,muscle,
intestinalmucosaandrenalcortex.Brainalsoswitchestousing
predominantlyacetoacetateinstarvation.
Inextrahepatictissues,acetoacetateisactivatedtoacetoacetylCoA
bysuccinyl-CoA-acetoacetateCoAtransferase(thiophorase).

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23.HGPRTareinvolve,andgoutcanbea
feature.
a)HGPRTdeficiency
b)HGPRToveractivity
c)PRPPsynthetasedeficiency
d)Glucose6-phosphatasedeficiency
e)Glucosephosphatedehydrogenasedeficiency
CorrectAnswer-A:D
Answer.(a)HGPRTdeficiency,(d)Glucose6-phosphatase
deficiency
[Ref:Harper30th/354-56;Satyanarayan4th/269-70,394-951
VonGierke'sdisease(Type1glycogenstoragedisease):
HyperuricemiaoccursduetoGlucose6-phosphataseenzyme
defect.
HGPRTdeficiency(asseeninLesch-Nyhansyndrome):Increased
productionofpurines
Glucose6-phosphatasedeficiency:Purineoverproduction.
Goutisusuallyprecededandaccompaniedbyhyperurlcemta
(plasmauricacidlevel>0.4Immol/L).
Hlperuricemiaiscausedbydacreasedrenalextretlon,lncreased
productlon"orincreasedintakeoturlcacid

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24.Hyperphenylalaninemiaoccursdueto:
a)Phenylalaninehydroxylasedeficiency
b)Phenylalaninehydroxylaseoveractivity
c)Dihydrobiopterinreductasedeficiency
d)Tyrosinehydroxylasedeficiency
e)Defectindihydrobiopterinbiosynthesis
CorrectAnswer-A:C:E
Answer:(a)Phenylalaninehydroxylase...,(c)Dihydrobiopterin
reductase...,(e)Defectindihydrobiopterinbiosynthesis
Hyperphenylalaninemiasarisefromdefectsinphenylalanine
hydroxylaseitself(typeI,classicphenylketonuriaorPKU),in
dihydrobiopterinreductase(typesIIandIII),orindihydrobiopterin
biosynthesis(typesIVandV).Alternativecatabolitesareexcreted.
PKUiscausedbyadcficiencyotphenylalaninehydroxyl.ase,isthe
mostcommonclinicallvencounteredinbornerrorofamino
acidmetabolism.
Hyperphenylalaninemiamayalsobecausedbydeficienciesinany
oftheseveralenzymesrequiredtosynthesizeBH4,or
indihydropteridinereductase,whichregeneratesBH4fromBH2.
BH4isalsorequiredfortyrosinehydroxylaseandtryptophan
hydroxylase,whichcatalyzereactionsleadingtothesynthesisof
neurotransmitters,suchasserotoninandreversethecentral
nervoussystem(CNS)effectsduetodeficienciesin
neurotransmitters.

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25.DuringDNAreplicationwhichbond
breaks:
a)Phosphodiesterbonds
b)Phosphatebond
c)Hydrogenbond
d)Glycosidicbonds
e)None
CorrectAnswer-C
Answer:c.Hydrogenbond[Ref:Lippincott6th/397-400;Harper
30th/381-86;Satyanarayana4th/524-29]
WhenDNAreplicates,ahelicaseenzyme"unzips"thedoublehelix,
breakingthehydrogenbondsthatholdittogetherinthecenter
Thetwostrandsofthedoublehelixseparatewhenhydrogenbonds
betweenthepairedbasesaredisrupted.Disruptioncanoccurinthe
laboratoryifthepHoftheDNAsolutionisalteredsothatthe
nucleotidebasesionize,orifthesolutionisheated.

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26.Oxidativephoephoryletlonnotinhiblted
by:
a)Fluoride
b)2,4-dinitrophenol(DNP)
c)Oligomycin
d)Carboxin
e)Ouabin
CorrectAnswer-A:D:E
Answer:(a)Fluoride,(d)Carboxin,(e)Ouabin(Ref:Harper
30th/132-33;Lippincott6th/79;Satyanarayan4th/233-34;
Chatterjea7th/132-341
TherearethreesitesinrespiratorychainwhereATPisformedby
oxidativephosphorylation.Threesitesare-Sitel(Complex-I),Site
Il(ComplexIII)andSiteIll(ComplexIV).Complexll(Succinate
dehyfuogenaseFAD)isnotinvolvedinoxidativephosphorylation.
2,4-dinitrophenol(DNP)Dinitrocresol,Trifluorocarbonylcyanide
phenylhydrazone,Pentachlorophenol
Aspirin(inhighdose),Highconcentrationofthermogenin,thyroxine
andlongchainfreefattyacids,Antibiotics-valinomycin,gramicidinA
andnigercinareinhibitoresofoxidativephosphorylation
CarboxininhibitcomplexII,whichisnotinvolvedinoxidative
phosphorylation(sonotincludedinanswer)"?Chatterjea7h/134
"OuabainisacardiacglycosidethatactsbyinhibitingtheNW/IC-
ATPasesodium-potassiumionpump"-Harper30th/491
Fluoride:Itinhibitstheactivitiesofcertainenzymes.Sodium
fluorideinhibitsenolase(ofglycolysis)whilefluoroacetateinhibits

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aconitase(ofcitricacidcycle)"-Satyanarayan4th/420.

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27.TrueaboutApolipoproteii.
a)Constituteperipheralregionofplasmalipoproteins
b)DividedintoA,B,Conly
c)ApoA-Iisthemajorproteincomponentofhighdensity
lipoprotein(HDL)
d)ApoA,BandCarefurtherdivided
e)Roleinenzymeactivation
CorrectAnswer-A:C:D:E
Answer.(a)Constituteperipheralregionof...,(c)ApoA-Iisthe
majorprotein...,(d)ApoA,BandCare...,(e)Roleinenzyme...
[Ref:Harper30th/254-55;Satyanarayan4th/318;
http://noprniscairres.in/bitstream;onlinelibrary.wiley.com]
Apolipoproteins(apo)playveryimportantrolesinthesynthesisand
catabolismofplasmalipoproteins,inlipidtransport,andas
activatorsofcertainenzymesassociatedwithlipidandlipoprotein
metabolism
Apolipoproteinsaretheproteincomponentofplasma
lipoproteinswhichconsistofacoreoftriglyceridesandcholesterol
estersandaperipheralregionofphospholipid,sphingolipidand
protein.
ApoA-Iisthemajorproteincomponentofhighdensity
lipoprotein(HDL)andaminorcomponentofchylomicronsandvery
lowdensitylipoprotein(VLDL).
Apolipoproteinsaredividedbystructureandfunctionintofive
majorclasses,AthroughE,withmostclasseshaving
subclasses,forexample,apolipoprotein(orapo)A-IandapoC-
II.

---

---

28.whichnNAcontalneabnormalpurineand
pyrimidine:
a)tRNA
b)23SrRNA
c)16SrRNA
d)5SrRNA
e)mRNA
CorrectAnswer-A
Answer:a.tRNA
tRNAmoleculecontainahighpercentageofunusalbases,for
example,dihydrouracilandhaveextensiveintra-chainbasepairing
thatleadstocharacteristicsecondaryandtertiarystructure"-
Lippincott6th/418.
ThetRNAmoleculescontainahighpercentageofunusualbases
(forexample,dihydrouracil)andhaveextensiveintrachainbase-
pairingthatleadstocharacteristicsecondaryandtertiarystructure.
TransferRNAisuniqueamongnucleicacidsinitscontentof
"unusual"bases.Anunusualbaseisanypurineorpyrimidinering
excepttheusualA,G,C,andUfromwhichallRNAsare

---

29.Aminoacidscontaininghydroxylgroup:
a)Threonine
b)Tyrosine
c)Serine
d)Tryptophan
e)Valine
CorrectAnswer-A:B:C
Answer:(a)Threonine,(b)Tyrosine,(c)SerineLippincott6th/4
Serine,threonine,andtyrosineeachcontainapolarhydroxyl
groupthatcanparticipateinhydrogenbondformation.
Thesidechainsofasparagineandglutamineeachcontainacarbon
ylgroupandanamidegroup,bothofwhichcanalsoparticipatein
hydrogenbonds"-

---

30.CytochromeP45Ois/areinvolvedln:
a)Hydroxylationofxenobiotics
b)Methylationofxenobiotics
c)Deaminationreaction
d)Involvedinhydroxylationofsteroids
e)Druginteraction
CorrectAnswer-A:C:D:E
Ans.(a)Hydroxylationofxenobiotics,(c)Deaminationreaction,
(d)Involvedinhydroxylationofsteroids,(e)Druginteraction
[Ref:Harper30th/584-85;KDT7th/23-26;Lippincott6th/;
Satyanarayan4th/639-40]
CytochromeP450sareinvolvedinphaseI(hydroxulation)ofthe
metabolismofxenobiotics,notinphaseII.Methylationof
xenobioticsoccurinphaseIIbymethyltransferase

---

31.Componentof50Sribosomalzubunit:
a)16SRNA
b)18SRNA
c)5.8RNA
d)5SRNA
e)23SRNA
CorrectAnswer-D:E
Answerd.5SRNA,(e)23SRNA(Lippincott6th/436):
The50Ssubunitisprimarilycomposedofproteinsbutalsocontains
single-strandedRNAknownasribosomalRNA(rRNA).rRNAforms
secondaryandtertiarystructurestomaintainthestructureandcarry
outthecatalyticfunctionsoftheribosome.
Itincludesthe5SribosomalRNAand23SribosomalRNA.
50Sincludestheactivitythatcatalyzespeptidebondformation
(peptidyltransferreaction),preventsprematurepolypeptide
hydrolysis,providesabindingsitefortheG-proteinfactors(assists
initiation,elongation,andtermination),andhelpsproteinfoldingafter
synthesis.

---

32.Trueaboutroleofphospholipids:
a)Celltocellrecognition
b)Cellsignaling
c)PrecursorofSecondMessengers
d)Mediatorsofinflammation
e)Regulatemembranepermeability
CorrectAnswer-B:C:D:E
Answer:(b)Cellsignaling,(c)PrecursorofSecond
Messengers,(d)Mediatorsofinflammation,(e)Regulate
membranepermeability
(Ref:Harper30th/212,216,253-54;Robbins9th/83-84;
Satyanarayan4th/36-37)
Glycoprotein(fibronectin,laminin)isinvolveincell-cell
recognitionandadhesion.
Theinositolispresentinphosphatidylinositolasthestereoisomer,
myoinositol.Phosphorylated
phosphatidylinositols(phosphoinositides)areminorcomponentsof
cellmembranes,butplayanimportantpartincellsignalingand
membranetrafficking.
Sphingomyelinsarealsofoundinlargequantitiesinthemyelin
sheaththatsurroundsnervefibers.Theyarebelievedtoplaya
roleincellsignalingandinapoptosis.
Phosphatidylinositolisthesourceofsecondmessengers
inositoltriphosphateanddiacylglyceol,thatareinvovedthe
actionofsomehoromones.

---

33.Correctstatementaboutmembrane:
a)Phospholipidsundergorapidlateraldiffusion
b)Transversemovementoflipidsacrossthemembraneisfaster
thanprotein
c)Hydrophobiccoreofthephospholipidbilayerremainsconstantly
inmotionbecauseofrotationsaroundthebondsoflipidtails
d)Phospholipdsthathaveonefattyacylgroup,cannotformthe
bilayer
e)Phospholipidsspanwholebilayer
CorrectAnswer-A:C:D
Ans.a)Phospholipidsundergo...,(c)Hydrophobiccoreofthe
phospholipid...,(d)Phospholipdsthathaveonefattyacyl...
(Ref:Harper30th/215-17,478-90;Satyanarayan4th/650-51;
en.wikibooks.org]
Membranesaremainlymadeupoflipids,proteinsandsmallamount
ofcarbohydrate.Phospholipidsarethemostcommonlipidspresent
andtheyareamphipathicinnature.
Thehydrophobiccoreofthephospholipidbilayerisconstantlyin
motionbecauseofrotationsaroundthebondsoflipidtails.
Hydrophobictailsofabilayerbendandlocktogether.However,
becauseofhydrogenbondingwithwater,thehydrophilichead
groupsexhibitlessmovementastheirrotationandmobilityare
constrained.Thisresultsinincreasingviscosityofthelipidbilayer
closertothehydrophilicheads.
Thelysophosphollpi.dshaveonlyonefattyacylgroup,itcannotform
thebilayerasthepolarheadsaretoolarge,similarlycholesterolalso
cannotformbilayersastherigidfitsedringsystenxsandadditional

---

nonpolartailsaretoolarge".

---

34.TrueaboutChromatin,remodeling:
a)EnergyisrequiredtodisplacethehistoneoctamersfromDNA
ortranslocatethemontoneighboringDNAsegments
b)Histonemodificationsbyspecificenzyme
c)Donotinvolveenzymes
d)Aberrationsinchromatinremodelingproteinsmaybe
associatedwithcancer
e)None
CorrectAnswer-A:B:D
Answer:aEnergyisrequiredtodisplacethehistone...,(b)
Histonemodificationsby...,(d)Aberrationsinchromatin...
[Ref:Harper30th/735,438-39;Lippincott6th/422,460;Harrison
19th/102e-7]
Chromatinremodelingisthedynamicmodificationof
chromatinarchitecturetoallowaccessofcondensedgenomic
DNAtotheregulatorytranscriptionmachineryproteins,and
therebycontrolgeneexpression.
chromatinremodelingcomplexesdisplacethehistone
octamersfromDNAortranslocatethemontoneighboringDNA
segments,therebyexposingunderlyingDNAsequencesto
sequencespecificregulatoryfactors.
histoneacetylaseandotherenzymaticactivitiesareassociated
withthecoregulatorsinvolvedinregulationofgene
transcription.
Aberrationsinchromatinremodelingproteinsarefoundtobe
associatedwithhumandiseases,includingcancer.

---

35.Bestassessmentofproteinbinding
regionsonaDNAmoleculecanbedone
by:
a)DNAfootprinting
b)RTPCR
c)Microarray
d)Westernblotting
e)Northernblotting
CorrectAnswer-A
Answer-(a)DNAfootprinting[Ref:www.biotecharticles.com;
www.biologyexams4u.comLippincott6th/473]
DNAfootprinting-Anin-vitrotechniquetofindoutprotein
bindingregionsonaDNAmolecule.Thetechniqueisalso
calledasDNAseIfootprinting.Thousandsofproteins
(enzymes)areinteractingwithDNAinthenucleusfor
regulatingactivitieslikereplication,transcription,translation
etc.
DNAFootprintingisamoleculartechniqueusedtoidentifythe
specificDNAsequence(bindingsite)thatbindstoaprotein.
Thistechniquemainlyusedtoidentifythetranscriptionfactors
whichbindtopromoter,enhancerorsilencerregionofgeneto
regulateitsexpression.Thereforetheregulationoftranscript
ionofagenecanbestudiedusingthismethod.

---

36.Nucleosomecontains:
a)DNA
b)RNA
c)Chromatin
d)Histone
e)None
CorrectAnswer-A:D
Ans:a.DNAd.Histone[RefHarper30th/371-72;Lippincott6th/
409]
Histonesarehighlyalkalineproteinsfoundineukaryoticcellnuclei
thatpackageandordertheDNAintostructuralunitscalled
nucleosomes.
Theyarethechiefproteincomponentsofchromatin,actingas
spoolsaroundwhichDNAwinds,andplayingaroleingene
regulation.
WhenthehistoneoctamerismixedwithpurifieddsDNAunder
appropriateionicconditions,thesamex-raydiffractionpatternis
formedasthatobservedinfreshlyisolatedchromatin.Biochemical
andelectronmicroscopicstudiesconfirmtheexistenceof
reconstitutednucleosomes.
Inthenucleosome,theDNAissupercoiledinalefthandedhelix
overthesurfaceofthedisk-shapedhistoneoctamer

---

37.EnzymeusedinDNArepairis/are:
a)DNAgyrase
b)DNApolymerase
c)Restrictionendonuclease
d)DNAligase
e)None
CorrectAnswer-B:D
Ans:b.DNApoly...,d.DNA(RefHarper30th/382,389-92;
Lippincott6th/411-131
Whenthestrandcontainingthemismatchisidentified,an
endonucleasenicksthestrandandthemismatchednucleotide(s)
is/areremovedbyanexonuclease.
Additionalnucleotidesatthe5'-and3'-endsofthemismatchare
alsoremoved.Thegapleftbyremovalofthenucleotidesisfilled,
usingthesisterstrandasatemplate,byaDNApolymerase.
The3'-hydroxylofthenewlysynthesizedDNAisjoinedtothe5'-
phosphateoftheremainingstretchoftheoriginalDNAstrandby
DNAligase

---

38.AllareUreacycleenzymesexcept:
a)Ornithinetranscarbamylase
b)Carbamoyl-phosphatesynthetaseI
c)Argininosuccinase
d)Citrullinesynthase
e)Argininosuccinicacidsynthetase
CorrectAnswer-D
Answer:(D)Citrullinesynthase[RefHarper30th/290-96,
29th/274-88;Lippincott

---

39.PhospholipaseA2acton:
a)Phosphoglycericacid
b)Phosphate
c)Ca+
d)Phosphatidyl-inositol
e)None
CorrectAnswer-D
Ans:d.Phosphatidyl-inositol
Phospholipaseshydrolyzethephosphodiesterbondsof
phosphoglycerides,witheachenzymecleavingthephospholipidata
specificsite.
Phospholipasesreleasemoleculesthatcanserveasmessengers
(forexample,DAGandIP3),orthatarethesubstratesforsynthesis
ofmessengers(forexample,arachidonicacid.
Phospholipasesareresponsiblenotonlyfordegrading
phospholipids,butalsofor"remodeling"them.Forexample,
phospholipasesAlandA2removespecificfattyacidsfrom
membrane-boundphospholipids;thesecanbereplacedwith
alternativefattyacidsusingfattyacylCoAtransferase.

---

40.Non-polaraminoacidsare:
a)Proline
b)Lysine
c)Isoleucine
d)Arginine
e)Asparginine
CorrectAnswer-A:C
Ans:a.Prolinec.Isoleucine[RefHarper30th/16-22;Lippincott
6th/1-9;Satyanarayan4th/48]
AcidicandPolarsidechainsAsparticAcidGlutamicAcid
BasicandPolarsidechainsArginine,Lysine,Histidine
Uncharged&PolarsidechainsAsparginine,Glutamine,Serine,
Threonine,Tyrosine
NonPolarAminoAcidswithNonPolarsidechainsGlycine,
Alanine,Valine,Leucine,Isoleucine,Proline.

---

41.Trueaboutsqualene:
a)Presentinsubhumanprimateonly
b)Itisoneofthemajorcarbohydratesofbody
c)Itinvolvesinthesynthesisofcholesterol
d)Itinvolvesinthesynthesisofsteroids
e)None
CorrectAnswer-C:D
Ans:(C)Itinvolvesinsynthesisofcholesterol,(D)Itinvolvesin
synthesisofsteroids
Squaleneisahydrocarbonandatriterpene,andisanaturaland
vitalpartofthesynthesisofallplantandanimalsterols,including
cholesterol,steroidhormones,andvitaminDinthehumanbody.
Squaleneisusedincosmetics,andmorerecentlyasan
immunologicadjuvantinvaccines.
Itisanatural30-carbonorganiccompoundoriginallyobtainedfor
commercialpurposesprimarilyfromsharkliveroil(henceitsname),
althoughplantsources(primarilyvegetableoils)arenowusedas
well,includingamaranthseed,ricebran,wheatgerm,andolives.
Squaleneandomega2fattyacidhasunlikeomega3fishoilsmore
completeandeffectivechemicalgroups.

---

42.Molecularweightofproteincanbe
determined/estimatedby:
a)SDS-PAGE
b)Gelfiltrationchromatography
c)Agarosegelelectrophoresis
d)Ultracentrifugation
e)FRETmicroscopy
CorrectAnswer-A:B:D
Ans:(A)SDS-PAGE(B)Gelfiltrationchromatography(D)
Ultracentrifugation[RefHarper30th/28;Shinde7th/772-74;
Satyanarayan4th/725,60;Vasudevan5th/482-851
"SDS-PAGEiscommonlyusedformolecularweightdetermination
ofproteins"(Vasudevan5th/482)
"SDS-PAGEisapopulartechniquefordeterminationofmolecular
weightofproteins"(Satyanarayan4th/725)
"Sodiumdodecylsulfate-polyacrylamidegelelectrophoresis(SDS-
PAGE)isareliablemethodfordeterminingthemolecular
weight(MW)ofanunknownprotein".
"Thegelfiltrationchromatographytechniqueisusedfor"Separation
ofproteinmolecules,purificationofproteins&molecularweight
determinations"Ultracentrifugationisanindispensabletoolforthe
isolationofsubcellularorganelles,proteins,&nucleicacids.In
addition,thistechniqueisalsoemployedindeterminationof
molecularweightofmacromolecules\

---

43.GelusedinRNAelectrophoresis:
a)Agarosegel
b)Polyacrylamideplaingel
c)PolyacrylamideSDS(Sodiumdodecylsulphate)impregnated
Polyacrylamidegel
d)A&C
e)None
CorrectAnswer-A
Ans:a.Agarosegel
SeparationofRNAinagarosegelsisusedforanumberofdifferent
purposes,includingNorthernblotstomonitorRNAexpression
levels,checkingRNAintegrityandsizeselectionofRNAforcloning
experiments.
SeparationofRNAbasedonfragmentlengthrequiresconditions
thataredifferentfromDNAanalysis.
ThemostfrequentlyuseddenaturantsforRNAagarosegel
electrophoresisareformaldehyde,formaldehyde/formamide,and
glyoxalplusDMSO.
ThemostefficientRNAdenaturantismethylmercuryhydroxide.
Becauseofthehazardsassociatedwiththisdenaturant,itisthe
leastusedsystemforRNA

---

44.Whichoffollowingreleases/provide
energy:
a)ConversionofADPtoATP
b)Breakingofhighenergybondtolowenergybond
c)Conversionofpyruvatetolactate
d)Electricalgradientacrossinner&outersideofmitochondria]
membrane
e)Passageofe-throughFADinelectrontransportchain
CorrectAnswer-B:D:E
Ans:(B)Breakingofhigh...(D)Electricalgradientacross...(E)
Passageofe-throughFAD....
Inabsenceof0xygenpyruvateisreducedtolacticacid(without
producingATP).Inanaerobicglycolysis,pyruvateactsasa
temporaryH-store.
Itdehydrogenation(oxidizes),thereducedNADH+H+backto
oxidizedNAD+,sothatglycolysiscancontinueevenintheabsence
of02.Inpresenceof02,lacticacidcanbeoxidizedintopyruvicacid
again.
ElectrontransportiscoupledtothephosphorylationofADPbythe
transport("pumping")ofprotons(H+)acrosstheinnermitochondrial
membranefromthematrixtotheintermembranespaceat
ComplexesI,III,andIV.
Thisprocesscreatesanelectricalgradient(withmorepositive
chargesontheoutsideofthemembranethanontheinside)anda
pHgradient(theoutsideofthemembraneisatalowerpHthanthe
inside).

---

Theenergygeneratedbythisprotongradientissufficienttodrive
ATPsynthesis.Thus,theprotongradientservesasthecommon
intermediatethatcouplesoxidationtophosphorylation.

---

45.Restrictionendonucleasecleaves:
a)dsDNA
b)RNA
c)Histone
d)Protein
e)ssDNA
CorrectAnswer-A
Ans:a.dsDNA
Restrictionendonucleases(restrictionenzymes),which
cleavedouble-stranded(ds)DNAintosmaller,moremanageable
fragments,hasopenedthewayforDNAanalysis"
Restrictionenzyme(REorRestrictionEndonuclease)isanenzyme
thatcleavedouble-strandedDNAQatspecificrecognitionnucleotide
knownasrestrictionsitesQ
ThecutDNAfragmentsbyREmayhavestickyends(cohesive
ends)?orbluntsends?dependingonthemechanismusedby
enzyme
DNAfragmentswithstickyendsareparticularlyusefulfor
recombinantDNAexperiments(hybridorchimericDNAmolecules)
Restrictionenzymeisnamedaccordingtotheorganismfromwhich
itwasisolated

---

46.Trueaboutgeneticcode:
a)FollowMendelianlaw
b)Itistotalnumberofchromosomeinthebody
c)Itisnucleotidesequencewhichcodesforaminoacids
d)ItcodesforDNA
e)None
CorrectAnswer-C
Ans:c.Itisnucleotidesequencewhichcodesforaminoacids
MendelianGeneticsiswidelyregardedasthecornerstoneof
classicalgenetics.Itisasetofprimarybeliefsrelatingtothe
transmissionofhereditarycharacteristicsfromparentorganismsto
theiroffspring
Thegeneticcodeisadictionarythatidentifiesthecorrespondence
betweenasequenceofnucleotidebasesandasequenceofamino
acids.
TheNucleotideSequenceofanmRNAMoleculeConsistsofa
SeriesofCodonsThatSpecifytheAminoAcidSequenceofthe
EncodedProtein

---

47.Whichofthefollowingisfeature(s)of
diabeticketoacidosis:
a)Decreasedtriglyceridelevel
b)Increasedfattyacidlevel
c)TLipoprotein
d)Decreasedketonebodies
e)HighAniongapacidosis
CorrectAnswer-B:C:E
Ans:(B)Increasedfattyacidlevel(C)TLipoprotein(E)High
Aniongapacidosis[RefHarper30th/231;Lippincott6th/339,
345;Satyanarayan4th/481,682;Harrison19th/2417-18]
DKAischaracterizedbyhyperglycemia,ketosis,andmetabolic
acidosis(increasedaniongap)alongwithanumberofsecondary
metabolicderangements,Leukocytosis,hypertriglyceridemia,and
hyperlipoproteinemiaarecommonlyfoundaswell
Increasedlacticacidproductionalsocontributestotheacidosis.The
increasedfreefattyacidsincreasetriglycerideandVLDLproduction.
VLDLclearanceisalsoreducedbecausetheactivityofinsulin-
sensitivelipoproteinlipaseinmuscleandfatisdecreased.
Hypertriglyceridemiamaybesevereenoughtocausepancreatitis.
Reducedinsulinlevels,incombinationwithelevationsin
catecholaminesandgrowthhormone,increaselipolysisandthe
releaseoffreefattyacids.Normally,thesefreefattyacidsare
convertedtotriglyceridesorvery-low-densitylipoprotein(VLDL)in
theliver.

---

48.Secondmessengeris/are:
a)Ca2+
b)DNA
c)Histone
d)cDNA
e)None
CorrectAnswer-A
Ans:a.Ca2+[RefHarper30th/501,91-92,179,343;Lippincott
6th/94-951
Nucleotides,suchascyclicadenosinemono-phosphate(cAMP)and
cyclicguanosinemonophosphate(cGMP),serveassecond
messengersinsignaltransductionpathways.
Twoofthemostwidelyrecognizedsecondmessengersystemsare
thecalciumlphosphatidylinositolsystem,andtheadenylylcyclase
system,whichisparticularlyimportantinregulatingthepathwaysof
intermediarymetabolism.

---

49.Nucleicacidamplificationtechniquesare:
a)PCR
b)RealtimePCR
c)DNACloning
d)NextgenerationDNAsequencing
e)None
CorrectAnswer-A:B
Ans:a.PCR...,b.Realtime....[RefHarper30th/458;Robbins
9th/180;Lippincott6th/479;Harrison19th/150e-7;http://link.
springer.corn]
Real-timePCRautomatesthelaboriousprocessofamplificationby
quantitatingreactionproductsforeachsampleinevery
Cycle.
Thereareseveralmethodsforamplification(copying)ofsmall
numbersofmoleculesofnucleicacidtoreadilydetectablelevels.
TheseNAATsincludePCR,LCR,stranddisplacementamplification,
andself-sustainingsequencereplication.
Theamplifiednucleicacidcanbedetectedafterthereactionis
completeor(inreal-timedetection)asamplificationproceeds.The
sensitivityofNAATsisfargreaterthanthatoftraditionalassay
methodssuchasculture.

---

50.Whichofthefollowingis/aretrueabout
pHofsolution:
a)Absoluteconcentrationofacid&salt
b)Relativeconcentrationofacid&saltinsolution
c)IncreaseoftemperatureincreasespH
d)AriseinH+concentrationdecreasespH
e)None
CorrectAnswer-B:D
Ans:(B)Relativeconcentration...,(D)AriseinH*concentra
tion....
"WhenpHmeasuredatroomtemperaturethereisnodirect
correlationbetweenpHandtemperature.
AriseinH+concentrationdecreasespHwhileafallinH+
concentrationincreasespH.ThereverseistrueforOH-
concentration
Theratioofsalttoacidconcentration-Actualconcentrationsofsalta
acidinabuffersolutionmaybevaryingwidely,withnochangein
pH,solongastheratiooftheconcentrationsremainsthesame

---

51.Truestatement(s)aboutMagnetic-
activatedcellsorting:
a)Itisamethodtoseparatespecificcellfromcomplexmixture
b)Fluorescentdyesareuses
c)Antibody-coatedmagneticnanoparticlesareused
d)Antibodiesusedarespecificforcertaincellsurfacemarkers
e)Magneticfieldisapplied
CorrectAnswer-A:C:D:E
Ans:(A)Itisamethod...,(C)Antibody-coatedmagnetic...,(D)
Antibodiesusedare...,(E)Magneticfieldisappli...
MACS,isaproceduredevelopedbyMiltenyiBiotectoseparatecells
fromcomplexmixturesusingantibody-coatedmagneticnano
particles.
Theantibodiesarespecificforcertaincellsurfacemarkers,either
expressedonyourpopulationofinterest(positiveselection),or
expressedonundesiredcelltypes(negativeselection).
Afteraddingtheantibody-coatedbeadstothecellmixtureand
incubating,thesuspensionisaddedtoaspecialsingle-use
separationcolumnaffixedtoamagnet,towhichthebeadsstick,
whileunlabeledcellsflowthrough.

---

52.Whichofthefollowingis/aretrueabout
Translation:
a)N-formylmethionineisfirstaminoacidinprokaryotes
b)UsesenergyinformofGMP
c)ElongationfactorEF-1&EF-2usedinprokaryotes
d)ElongationfactorPisusedineukaryoticorganism
e)Threeinitiationfactorsarerequiredinprokaryotes
CorrectAnswer-A:E
Ans:a.N-formylmethionine...,e.Threeinitiation[RefHarper
30th/419-23;Lippincott6th/438-42;Satyanarayan4th/554-60]
Ineukaryotes,thefirstaminoacidincorporatedismethionine(AUG
codon).Butinprokaryotes,thesamecodonattractsN-formyl
methionine,whichisthefirstaminoacid"(Vasudevan5th/432)
"ElongationfactorPisaprokaryoticproteintranslation
factorrequiredforefficientpeptidebondsynthesison70S
ribosomesfromfMet-tRNAfMet.Itprobablyfunctionsindirectlyby
alteringtheaffinityoftheribosomeforaminoacyl-tRNA,thus
increasingtheirreactivityasacceptorsforpeptidylStepsinProtein
Synthesis
Inprokaryotes,threeinitiationfactorsareknown(IF-1,IF-2,andIF-
3),whereasineukaryotes,thereareoverten(designatedeIFto
indicateeukaryoticorigin).EukaryotesalsorequireATPforinitiation.

---

53.TwostrandsofDNAis/areheldby:
a)Glycosidicbond
b)Hydrogenbond
c)Covalentbond
d)Ionicbond
e)Vanderwaalforce
CorrectAnswer-B
Answer(b)hydrogenbond[RefHarper30th/359;Lippincott
6th/396-97;Satyanarayan4th/75]
Thetwostrandsareheldtogetherbyhydrogenbondformed
bycomplementarybasepairs"(Satyanarayan4th/75)
"Thebasepairsareheldtogetherbyhydrogenbonds:twobetween
AandTandthreebetweenGandC.Thesehydrogenbonds,plus
thehydrophobicinteractionsbetweenthestackedbases,stabilize
thestructureofthedoublehelix.

---

54.Silverstainingisdonefor:
a)DNA
b)RNA
c)Karyotypinganalysis
d)Protein
e)Collagen
CorrectAnswer-A:B:C:D:E
Answer-(A)DNA(B)RNA(C)Karyotypinganalysis(D)Protein
(E)Collagen
Silverstainingisahighlysensitivemethodfordetectingproteinsand
nucleicacids(dsDNA&RNA)inpolyacrylamideslabgels.
Silverstainingistheuseofsilvertoselectivelyaltertheappearance
ofatargetinmicroscopyofhistologicalsections;intemperature
gradientgelelectrophoresis;andinpolyacrylamidegels.
Silverstainingisthemostsensitivemethodforpermanentstaining
ofproteinsornucleicacidsinpolyacrylamidegels.
Histologicalcharacterization:Silverstainingaidsthevisualizationof
targetsofinterest,namelyintracellularandextracellularcellular
componentssuchasDNAandproteins,suchastypeIIIcollagen
andreticulinfibresbythedepositionofmetallicsilverparticlesonthe
targetsofinterest.

---

55.PolymeraseIIIsynthesizes:
a)Fragment28SofrRNA
b)Fragment23SofrRNA
c)Fragment5SofrRNA
d)tRNA
e)mRNA
CorrectAnswer-C:D
Ans:c.andd[RefHarper30th/395-98;Lippincott428]
"RNApolymeraseIIIsynthesizestRNA,5SrRNA,andsomesnRNA
andsnoRNA"(Lippincott428)

---

56.Non-codingRNAis/are:
a)miRNA
b)SiRNA
c)tRNA
d)mRNA
e)rRNA
CorrectAnswer-A:B:C:E
Ans:a.miRN...,b.SiRNA...,c.tRNA...,e.rRNA...,[RefHarper
30th/394-95,368;en.wikipedia.org;Lippincott6th/417]
AlleukaryoticcellshavetwomajorclassesofRNA,theprotein
codingRNAs,ormessengerRNAs(mRNAs),andtwoformsof
abundantnon-proteincodingRNAsdelineatedonthebasisofsize:
thelargeribosomalRNAs(rRNA)andlongnoncodingRNAs
(lncRNAs)andsmallnoncodingRNAstransferRNAs(tRNA),the
smallnuclearRNAs(snRNAs)andthemicroandsilencingRNAs
(miRNAsandsiRNAs).
ThemRNAs,rRNAsandtRNAsaredirectlyinvolvedinprotein
synthesiswhiletheotherRNAsareparticipateineithermRNA
splicing(SnRNAs)ormodulationofgeneexpressionbyaltering
mRNAfunction(mi/SiRNAs)and/orexpression(lncRNAs).These
RNAdifferintheirdiversity,stability,andabundanceincells

---

57.Trueaboutsuccinatedehydrogenase
defect-
a)DeficiencyofcomplexII
b)Tumorigenesis
c)Defectinkrebscycle
d)DefectinETC
e)Mitochondrialencephalopathy
CorrectAnswer-A:B:C:D:E
ANSWER-(A)DeficiencyofcomplexII(B)Tumorigenesis
(C)Defectinkrebscycle(D)DefectinETC(E)Mitochondrial
encephalopathy
Mitochondrialsuccinatedehydrogenase(SDH)catalysesthe
oxidationofsuccinatetofumarateintheKrebscycle(citricacid
cycle).
Succinatedehydrogenasecomplexismadeupoffoursubunits-(i)
SDH-A;(ii)SDH-B;(iii)SDH-C;and(iv)SDH-D.
Functionsofsuccinatedehydrogenaseare:?
1. CatalysesoxidationofsuccinateorfumarateinTCAcycle/citric
acidcycle.
2. TransferselectronsfromsuccinatetocoenzymeQ(atcomplex
II)SuccinatedehydrogenaseactsascomplexIIinETC.
DefectinSDHcausesdefectinmitochondrialETC.Whichleadsto
mitochondria!encephalopathyandmyopathy
(encephalomyopathy)ThisisduetomutationinSDHAsubunit
gene.
MutationinSDH-B,-Cand-Dsubunitscausestumorformation,

---

especiallyparaganglioma/pheochromocytoma/carotidbodytumor
Thus,thesesubunitsareregardedasatumorsuppressorgene.

---

58.Allaretrueaboutglycosaminoglycans
except?
a)Proteinassociatedwithglycosaminoglycansiscalledcore
proteins
b)Maybeassociatedwithconnectivetissues
c)Highlypositivelycharged
d)Negativelycharged
e)ComponentofECM
CorrectAnswer-C
Ans.is'c'i.e.,Highlypositivelycharged[RefHarper30"/ep.
786]
Proteoglycansarecarbohydratestowhichsmallamountofproteinis
attached.Proteoglycansconsistsof95%ofcarbohydratesand5%
ofprotein.Toknowthestructureofproteoglycans,oneshouldknow
thestructureofglycosaminoglycans.
Glycosaminoglycansareheteropolysaccharide
(heteropolysaccharidesarepolysaccharideswhichcontaintwoor
moredifferentmonosaccharideunitortheirderivatives).
Glycosaminoglycansarelinear(unbranched)polysaccharides,with
repeatingdiasaccharideunits.Eachdisaccharideunitconsistsofan
aminosugarandanacidsugar(sugaracid).
Glycosaminoglyclanswerefirstisolatedfrommucin,thereforethey
arealsocalledmucopolysaccharides.
Theyarenegativelycharged.

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59.Mechanismsforregulatingenzyme
activityareALLEXCEPT
a)Covalentmodification
b)Allostericactivation
c)Competitiveinhibition
d)Inductionofgenesforenzymesynthesis
e)Repressionofgeneforinhibitionofenzymesynthesis
CorrectAnswer-C
Ans.is(c)Competitiveinhibition[Ref:Harper319`Vep.89-
94;Lippincott6"/ep.62-64;Vasudevan5thiep.42-50;Shinde
Asthenamesuggests,thereiscompetitionbetweeninhibitorand
normalsubstrateforthecatalyticbindingsiteoftheenzyme.Thisis
becauseboththeinhibitorandthenormalsubstratehavesimilar
structuralconfiguration.Therefore,enzymecannotdifferentiate
thesetwoandbothcanbindtotheenzyme.BothESandEI
complexesareformed.ButonlyEScanformproduct.

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60.Truestatementare-
a)Alllipidarefat
b)Linoleicacidisessentialfattyacid
c)Hydrogenationconvertsunsaturatedfattyacidtosaturated
fattyacid
d)Rancidityoffoodisduetolipidperoxidation
e)Hydrolysisoffatbyacidissaponification.
CorrectAnswer-B:C:D
Ans.is"B"i.e.,Linoleicacidisessentialfattyacid;"C"
Hydrogenationconvertsunsaturatedfattyacidtosaturated
fattyacid;'d'i.e.,Rancidityoffoodisduetolipid
peroxidation[RefLippincott6"Iep.181-1821.
Thethreepolyunsaturatedfattyacids(PUFAs),namely,linoleicacid
linolenicacidandarachidonicacidarecalledessentialfattyacids.
theyarecalledessentialfattyacidsbecausehumanbeingsrequire
thesefattyacidsbutcannotsynthesizethem.
Additionofhydrogenatomstounsaturatedfattyacidrefersto
hydrogenation.Itreducesthenumberofdoublebondsin
unsaturatedfats,Ashydrogenationreducesnumberofdouble
bonds,unsaturatedfattyacidsmaygetconvertedtosaturatedfatty
acid,ifalldoublebondsarereduced.
Theunpleasantodorandtaste,developedbynaturalfatsupon
aging,isreferredtoas"rancidity".Ranciditymaybedueto
hydrolysis(bylipase)oroxidationoffat.

---

61.Truestatement(s)aboutlipiddigestion
andabsorption-
a)Micellesplayanimportantroleinlipidsabsorption
b)Absorptionoflong-chainfattyacidsisgreatestintheupper
partsofthesmallintestine
c)Bileacidhasnoroleinfatabsorption
d)Fattyacidsafterabsorptionarereesterifiedtotriglycerides
intheenterocytes
e)Gastriclipaseisthemajorenzyme
CorrectAnswer-A:B:D
Ans.is'a'i.e.,Micellesplayanimportantroleinlipids
absorption;'b'i.e.,Absorptionoflong-chainfattyacidsis
greatestintheupperpartsofthesmallintestine;&'d'Le.,Fatty
acidsafterabsorptionarereesterifiedtotriglyceridesinthe
enterocytes[RefGanong251h/ep.481-83;Harper..30thlep.
253-54;Guyton12thIep.421-23;Lippincott6th/ep.1761.
Micellesformationistheprocessinwhichdigestedfats(FFAsand
monoglycerides)areincorporatedintomuchsmallerdroplets
(micelles)sothattheycanbeabsorbedmoreefficiently.Thus,
micellesformationhelpsinabsorptionofdigestedfats.
Fatdigestionessentiallybeginsintheduodenumwithentryof
pancreaticandbiliarysecretions.Pancreaticjuicecontainslipase
(pancreaticlipase),themostimportantenzymeforfatdigestion.The
pancreaticlipasedigeststriglycerides(triacylglycerols)intofreefatty
acidsand2-monoglycerides(2-monoacylglycerols).
Afterfatdigestion,fattyacidsandmonoglyceridesareabsorbedin

---

thesmallintestine,especiallyinthejejunumandsomeamountalso
inileum.Insidetheenterocyte,fattyacidsandmonoglycerides
againformtriglycerides.

---

62.Gluconeogenesisisfavouredinfasting
stateby-
a)ActivationofpyruvatecarboxylasebyacetylCoA
b)Increasedconversionofphosphoenolpyruvatetopyruvate
byactivationofpyruvatekinase
c)Increasedfattyacidoxidationinliver
d)Hydrolysisoffructosel,6-bisphosphatebyfructosel,6-
bisphosphatase
e)None
CorrectAnswer-A:C:D
Ans.is'a'i.e.,Activationofpyruvatecarboxylasebyacetyl
CoA;'c'i.e.,Increasedfattyacidoxidationinliver;'d'i.e.,
Hydrolysisoffructose1,6-bisphosphatebyfructose1,6-
bisphosphatase,
[Ref:Satyanarayan4thiep.258-63;Harper30thiep.188;
Lippincott6fVep.117-123;Shinde7m/ep.347]
Theactivationofpyruvatecarboxylaseandreciprocalinhibitionof
PDHcomplexbyacetyl-CoAderivedfromtheoxidationoffattyacids
explaintheactionoffattyacidoxidationinsparingtheoxidationof
pyruvateandinstimulatinggluconeogenesis.
Thereciprocalrelationshipbetweenthesetwoenzymesaltersthe
metabolicfateofpyruvateasthetissuechangesfromcarbohydrate
oxidation(glycolysis)togluconeogenesisduringthetransitionfrom
thefedtofastingstate.
Fructose-2-6-bisphosphateisformedbyphosphorylationoffructose-
6-phosphatebyphosphofructokinase-2.Thisenzymeisa

---

bifunctionalenzymethatalsohasfructose-2,6-bisphosphatase
activitywhichisresponsibleforbreakdownoffructose-2,6-
bisphosphatasebacktofructose-6-phosphate.
Thisbifunctionalenzymeisunderallostericcontroloffructose-6
phosphatewhichstimulatesphosphofructokinase-2activityand
inhibitsfructose-2,6-bisphosphataseactivity.

---

63.AIIaretrueaboutHexose
monophosphatepathway(HMP)except-
a)ProduceNADPHinoxidativephaseofpathway
b)DoesnotproduceATP
c)Occursintestes,ovaries,placentaandadrenalcortex
d)Producesribose5-phosphateinoxidativephaseofpathway
e)Glucose6-phosphatedehydrogenaseenzymeisinvolved
CorrectAnswer-D
Ansis.'d'i.e.,Producesribose5-phosphateinoxidativephase
ofpathway[RefHarper30thiep.196-200;Lippincottelep.145;
Satyanarayan4thIep.270-71]
HMPshuntisamulticyclicprocessinwhich3moleculesofglucose-
6-phosphategiveriseto3moleculesofCO,and3moleculesof5-
carbonsugars(ribulose-5-phosphate).
Thelatterarerearrangedtogenerate2moleculesofglucose-6-
phosphate(throughfructose-6-phosphate)and1molecule
glyceraldehyde-3-phosphate.HMPshuntdoesnotgenerateATP.
HMPshuntoccursinthecytosol.Itishighlyactiveinliver,adipose
tissue,adrenalcortex,lens,cornea,lactating(butnotthe
nonlactating)mammarygland,Gonads(testis,ovary)and
erythrocytes.Activityofthispathwayisminimalinmuscleandbrain,
wherealmostalloftheglucoseisdegradedbyglycolysis.

---

64.Post-translationmodificationofprotein
includesallexcept:
a)Removalofpeptide
b)5'capping
c)Intronsplicing
d)Proteinfolding
e)Covalentmodification
CorrectAnswer-B:C
Ans.isB.,5'capping&`ci.e.,intronsplicing[Ref;
Satyanarayan4thiep.561-62;Harper30`lep426;Lippincott0-
4p.443-441
5'cappingandintronsplicingarepost-transcriptionalmodification
(notpost-translationalmodification.
Thisisthefirstprocessingreaction.5'-endofmRNAiscappedwith
7-methylguansosine.
Thiscaphelpsininitiationoftranslation(proteinsynthesis)and
stabilizesthestructureofmRNAbyprotectingfrom5'-exonuclease
Removalofintrons(splicing):?Eukaryoticgenescontainsome
codingsequenceswhichcodeforproteinandsomeinterveningnon-
codingsequenceswhichdonotcodeforprotein.

---

65.Whichofthefollowingisnottrueabout
transcription
a)SynthesisofprecursorsforthelargeandsmallribosomalRNAs
b)FormationoftRNAtranscript
c)RNApolymeraseIIisresponsibleforthesynthesisof
precursorsforthelargeribosomalRNAs
d)RNApolymeraseIisresponsibleforthesynthesissmall
ribosomalRNAs
e)BindingofRNApolymeraseonDNA
CorrectAnswer-C:D
Ans.is'c'i.e.,RNApolymeraseIIisresponsibleforthe
synthesisofprecursorsforthelargeribosomalRNAs;&'d'i.e.,
RNApolymeraseIisresponsibleforthesynthesissmall
ribosomalRNAs.
[Ref:Harrion19th/ep.427-28;Satyanarayan4thiep.546,566-68]
RNA,eukaryoteshavethreedifferentRNApolymerases:I,II,II
RNApolymeraseI:Itcatalyzesthesynthesisoflargeribosomal
RNA(rRNA),i.e.28SrRNA,18SrRNAand5.8SrRNA.
TheserRNAsarecodedonclass-Igene,i.e.classIgeneis
transcribedbyrRNA.rRNAsarenottranslatedintoprotein.
RNApolymeraseII:?ItcatalyzesthesynthesisofmRNA,small
nuclearRNA(sn-RNA)andmiRNA.Theseproductsarecodedby
classIIgene,i.e.classIIgeneistranscribedbymRNA.ClassII
genedifferfromclassIandIIIinthatoneofitstranscribedproducts
(mRNA)istranslatedintoprotein
RNApolymeraseIII:?ItcatalyzesthesynthesisoftRNAand5S

---

rRNA.TheseproductsarecodedbyclassIIIgene.
BesidesthesethreenuclearRNApolymerases,inaeukaryoticcell,
afourthtypeofRNApolymeraseisfoundinmitochondrialmatrix
knownasmitochondrialRNApolymerase(mtRNAP).Similarto
prokaryoticRNApolymerase,mtRNAPcatalyzesthesynthesisofall
thethreetypesofRNA,i.e.mRNA,tRNAandrRNA

---

66.Ultravioletradiationexposurecancauses
DNAdamageby-
a)Pyrimidinedimersformation
b)DNAbreakage
c)Thyminedimerformation
d)AcetylationofDNA
e)MethylationofDNA
CorrectAnswer-A:C
Ans.is'a'Pyrimidinedimersformation;&'c'i.e.,Thyminedimer
formation[RefHarper30/ep.761;Lippincott0/ep.412]
UVraysexposureresultsincovalentjoiningoftwoadjacent
pyrimidines(usuallythymine)toformpyrimidinedimers(thymine-
thyminedimersorcyclobutanepyrimidinedimers).Cytosine-
thymineandcytosine-cytosinedimersarealsoformedbutatslower
rates.
Ultravialet(UV)radiations:-Inducedimerizationofadjacent
pyrimidinestoproducepyrimidinedimers.

---

67.TrueaboutDNAphotolyase-
a)RepairdamagecausedbyUVlight
b)Foundonlyinhuman
c)Usevisiblelight
d)Breakspyrimidinedimers
e)None
CorrectAnswer-A:C:D
Ans.is'a'i.e.,RepairdamagecausedbyUVlight;'c'i.e.,Use
visiblelight;&'d'Breakspyrimidinedimer[Ref:PankajNaikp.
496]
NearlyallcellscontainaphotoreactivatingenzymecalledDNA
photolyase.ItisaDNArepairenzymewhichbindtothedamaged
regionofDNAandgetexcitedbylightenergyabsorbedbyN5,N'?-
methenyltetrahydrofolate,whichisboundtothephotolyase.The
processiscalledphotoreactivation.
Theactivationrequiresvisiblelight,preferentiallyfromtheviolet/blue
endofthespectrum.
Theexcitedphotolyasethencleavesthedimerintooriginalbases.
Theseenzymesoccurinalmostalllivingorganismsexposedto
sunlight,theonlyexceptionbeingplacentalmammalslikehumans
andmice.Theircatalyticmechanismemploysthelight-driven
injectionofanelectronintotheDNAlesiontotriggerthecleavageof
cyclobutane-pyrimidinedimers.
PhotolyaseisparticularlyimportantinrepairingUVinduceddamage
inplants.Thephotolyasemechanismisnolongerworkingin
humansandotherplacentalmammalswhoinsteadrelyontheless
efficientnucleotideexcisionrepairmechanism.

---

---

68.TrueaboutDNAGyrase-
a)AtypeoftopoisomeraseI
b)AtypeoftopoisomeraseII
c)ActoncircularDNA
d)Overcometheproblemofsupercoils
e)None
CorrectAnswer-B:C:D
Ans.is'b'i.e.,AtypeoftopoisomeraseIL;"c'i.e.,Acton
circularDNA;'d',Overcometheproblemofsupercoils
[RefLippincottetc401;StayanarayanxlaVep.528J
TopoisomeraseI4Removesnegativesupercoiling.
TopoisomeraseIIRelaxespositivesupercoilsandformsnegative
supercoilingbycondensation.ofchromosome.
TopoisomeraseIIICanintroducesinglestrandbreaksduring
recombinationthatarerequiredforDNAtobeexchanged.

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69.Whichofthefollowingenzymesofurea
cycleis/arenotpresentinmitochondria?
a)Carbamoylphosphatesynthetase-1[CPS-1]
b)Arginase
c)Arginosuccinase
d)Arginosuccinatesynthase
e)Ornithinetranscarbamylase
CorrectAnswer-B:C:D
Ans.is'b'i.e.,Arginase,'c'i.e.,Arginosuccinase&'d'i.e.
Arginosuccinatesynthase[RefHarper's30th/ep.291]
Ammoniaisultimatelydisposedofbyformationofureaby"Kreb's
Henseleitureacycle"intheliver.
Ureacycletakesplacebothinmitochondriaandcytosol.
Firsttworeactionsofureacycleoccurinthemitochondria,and
remainingreactionsoccursincytosol
Argininosuccinatesynthasecatalyzestheformationof
argininosuccinatefromcitrullineandaspartate.Thisreaction
requiresIATP,but2highenergyphosphatebondsareconsumedas
ATPisconvertedtoAMP+PPi.Theaminogroupofaspartate
providesoneofthetwonitrogenatomsthatappearinurea(The
otheroneisprovidedbyammoniaNH4).
Argininosuccinatelyase(argininosuccinase)catalysesthecleavage
ofargininosuccinateintoarginineandfumarate.Fumarateentersin
TCAcycle.
Arginasecatalysestheformationofureafromargininebyhydrolytic
cleavageofargininetoyieldureaandornithine.Ornithineisthus

---

regeneratedandcanentermitochondriatoinitiateanotherroundof
theureacycle.

---

70.Regulatoryenzymesofglycolysisare-
a)Phosphofructokinase
b)Pyruvatekinase
c)BPGkinase
d)Hexokinase
e)Glucose-6-phosphatase
CorrectAnswer-A:B:D
Ans.'a'i.e.,Phosphofructokinase,'b'i.e.,Pyruvatekinase&'d'
i.e.,Hexokinase[RefHarper's30thlep.170-177]
Glycolysisisregulatedat3stepswhichareirreversible.These
reactionsarecatalyzedbyfollowingkeyenzymes:(1)Hexokinase
andglucokinase,(2)PhosphofructokinaseI,and(3)Pyruvate
kinase.
Hexokinaseisfoundinmostofthetissueexceptliverandcomes
intoplaywhenbloodglucoseislow.Itisnotaffectedbyfeedingor
insulinorstarvation.Hexokinaseisnotspecificforglucose
metabolism,itisalsoinvolvedinmetabolismoffructoseand
galactose.
PhosphofructokinaseIisthemajorregulatoryenzymeofglycolysis.
Itcatalyzesthe3rdreactionofglycolysis,i.e.,fructose-6-P-a
Fructose1,6bis-P.Thisreactionisirreversibleandisthe"rate-
limitingstep"forglycolysis.
Itisallostericallyactivatedby:Fructose-6-phosphate,fructose2,6-
bisphophate,AMP,ADP,K.andphosphate.Itisallosterically
inhibitedby:ATP,citrate,Ca+2,Mg+2,andlowpH.
Phosphofructokinaseisaninducibleenzymethatincreasesits

---

synthesisinresponsetoinsulinanddecreasesinresponseto
glucagon.
PyruvatekinaseisenzymethatcatalyzesconversionofPEPto
pyruvate.Pyruvatekinaseisaninducibleenzymethatincreasesin
concentrationwithhighinsulinlevelanddecreaseswithglucagon.It
isactivatedbyfructose-1,6bisphosphateandinactivatedbyATP
andalanine.

---

71.Whichofthefollowingis/areto-6fatty
acid(s)
a)Linoleicacid
b)Arachidinicacid
c)Gammalinolenicacid
d)Alphalinolenicacid
e)Oleicacid
CorrectAnswer-A:B:C
Ans.is'a'i.e.,Linoleicacid,'b'i.e.,Arachidinicacid&'c'i.e.,
Gammalinolenicacid[Ref:Harper's30thlep.2141
Linoleicacid(18carbon:Chemicalformula'aCH,-(CH,),-CH=CH
-CH2-CH=CH-(CH2)7-COOH
C-SystemC:18:2:6,9'12orC:18:2:9,12,i.e.18carbonfattyacidwith
2doublebondsat915(betweenC-9andC-10)and12'(betweenC-
12andC-13)positionswhennumberingisstartedfromcarboxyl
carbon.
co-systemC:18:2:w-6,9,i.e.18carbonfattyacidwith2double
bondsat6th(betweenC-6andC-7)and9'(betweenC-9andC-10)
positionswhennumberingisstartedfromterminalmethylcarbon.So
linoleicacidisco-6fattyacid,asthefirstdoublebondisat6th
positioninco-systemclassification.
Arachidonicacid(20carbon)ChemicalformulaC20H32O2

---

72.Nonreducingsugarsareallexcept-
a)Glucose
b)Maltose
c)Sucrose
d)Fructose
e)Galactose
CorrectAnswer-A:B:D:E
Ans.is'a'i.e.,Glucose;b'i.e.,Maltose;'d'i.e.,Fructose&`e'
i.e.,Galactose[RepDineshPuri3"'/elep.24]
Reducingsugarsaresugarswhichhavefreealdehydeorketone
grouptheirintheirstructure.Becauseofthepresenceoffree
aldehydeorketonegroup,theycanreducecertainheavymetallic
cationsinanalkalimediumandintheprocesstheythemselvesget
oxidizedtoamixtureofsugaracids.
Glucoseandgalactosehavefreealdehydegroupatcarbon-1,and
fructosehasfreeketonegroupatcarbon-2.Thus,reducingendof
glucoseandgalactoseiscarbon-1andoffructoseiscarbon-2.
Sucrose(disaccharideofglucoseandfructose)isformeddueto
formationofa-glycosidicbondbetweencarbon-1ofglucoseand
carbon-2offructose(Glucose-al2-Fructose).Thus,reducing
endofbothglucose(carbon-1)andfructose(carbon-2)areinvolved
inglycosidicbondformationandthereforelosttheirreducing
property.Hence,sucroseisanon-reducingdisaccharide.

---

73.ApointegratedinHDLis-
a)ApoAl
b)ApoE
c)ApoD
d)ApoB48
e)ApoB100
CorrectAnswer-A:B:C
Ans.is'a'i.e.,ApoAl;'b'i.e.,ApoE;&'c'i.e.,ApoD[Ref
Harper's30th/ep.257,255;Chatterjee6th/ep.382]
Apo-A1isfoundinHDL,Chylomicrons,siteofsynthesiisLiver,
intestine,andfunctioninMajorstructuralproteinofHDL,major
activatorofLCAT.
Apo-E(argininerich),foundin-Chylomicrons,chylomicron,siteof
synthesis-liver,functionasMediatesuptakeofchylomicron
remnantsandIDLbyLDLreceptorsinliver.
Apo-D--foundinHDL-Spleen,brain,testes,adrenal

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74.Poorwoundhealinginvitamin'C'
deficiencyisduetoallexcept-
a)Inhibitionofcollagensynthesis
b)Defectivecollagensynthesis
c)Defectivepost-translationalmodificationofcollagen
d)Defectivehydroxylation
e)Defectinantioxidantsystem
CorrectAnswer-A
Ans.is"a"Inhibitionofcollagensynthesis
Ascorbicacid(VitaminC)isalsocalledantiscorbuticfactor.Itisvery
heatlabile,especiallyinbasicmedium.Ascorbicaciditselfisan
activeform.MaximumamountofvitaminCisfoundinadrenal
cortex.
Ascorbicacidfunctionsasareducingagentandscavangeroffree
radicals(antioxidant).Itsmajorfunctionsare
1. vitaminCisessentialfortheconversionofprocollagentocollagen,
whichisrichinhydroxyprolineandhydroxylysine.Throughcollagen
synthesis,itplaysaroleintheformationofmatrixofbone,cartilage,
dentineandconnectivetissue.
2. VitaminCisrequiredforpost-translationalmodificationby
hydroxylationofprolineandlysineresiduesconvertingtheminto
hydroxyprolineandhydroxylysine.

---

75.MicroSatelliteinstabilityisseenin?
a)Huntington'sdisease
b)Lynchsyndrome
c)Spinocerebellarataxia
d)HNPCC
e)Colorectalcancer
CorrectAnswer-A:B:C:D:E
Ans.is'a'i.e.,Huntington'sdisease;'b'i.e.,Lynchsyndrome;
'c'i.e.,Spinocerebellarataxia;'d'i.e.,HNPCC;&'e'i.e.,
Colorectalcancer[RefTextbookofgeneticcounsellingp.712]
Microsatelliteinstabilityisgeneticinstabilityinshortnucleotide
repeats(microsatellites)duetohighmutationrateasaresultof
defectsinmismatchrepairofDNA.
Sometimesreplicationerrorsescapetheproofreadingfunction
duringDNAsynthesiscausingamismatchofoneofseveralbases.
Theseerrorsarerepairedlater.
Animportantpointisthattherepairsystemmustbeableto
discriminatebetweentheparent(template)strandandthenew
daughterstrandbecauseitisthebaseonthedaughterstrandparent
thatisincorrectsoneedstobeexcised.
Methylgrouponparentstrandattachedtoadenine(methylated
adenine)nearthemismatchservesasatagbywhichtherepair
systemidentifies.
SeveralNeurologicaldiseasearecharacterizedbymicrosatellite
sequenceinstabilityincludingHuntington'sdisease,myotonic
dystrophy,Fragile-Xsyndrome,Friedreich'sataxiaand
spinocerebellarataxia.

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---

76.UDP-glucoseisusedfor-
a)Glycogensynthesis
b)Galactosemetabolism
c)Bilirubinmetabolism
d)Gangliosidesynthesis
e)Heparinsynthesis
CorrectAnswer-A:B:C:E
Ans.is'a'i.e.,Glycogensynthesis;'b'i.e.,Galactose
metabolism;'c'i.e.,Bilirubinmetabolism;&`e'i.e.,Heparin
synthesis[RefBasicmedicalbiochemistryp.475]
UDP-glucoseisderivedfromglucose-6-phosphateviaglucose-l-
phosphate.
ThemajorfateofUDP-glucoseisthesynthesisofglycogen.
OtherusesofUDP-glucoseare-
1. Inuronicacid(glucoronicacid)cycletogenerateUDPglucuronate.
2. Galactosemetabolism
Glycosylationofproteins,lipidsandproteoglycans.
UDPglucuronate(whichisderivedfromUDPglucose)isusedfor:-
1. Conjugationofbilirubin,benzoicacid,sterols,estrogenanddrugs.
2. Biosynthesis

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77.ComplementaryDNAdiffersfromgenomic
DNAin-
a)Hascodedsegments
b)Hasintrons
c)Hasonlyexons
d)Usesreversetranscriptase
e)Larger
CorrectAnswer-A:C:D
Ans.is'a'i.e.,Hascodedsegments;'c'i.e.,Hasonlyexons;&
'd'i.e.,Usesreversetranscriptase.[Ref:Lehninger5"Yep.940-
9601
Collectionofcloned(recombinant)DNAfragmentsiscalledDNA
libraryorshotguncollection.DNAlibrariesmaybeoftwotypes?
1)Genomiclibrary:-
TheentiregenomicDNA(bothexonsandintrons)ofanorganismis
cutintosmallpiecesbyrestrictionendonucleases.
Eachandeveryfragmentisthenclonedwithsuitablevector.These
recombinantclonesarethencollected.
2)ComplementaryDNA(cDNA)library:-
IncDNAlibraryonlyexonsarerepresented.Itisconstructedsoas
toincludeonlythosegenesthatareexpressed.
cDNAlibraryismorespecializedandexclusiveDNAlibrary.
ThemRNAsfromanorganismisextractedandcomplementary
doublestrandedDNAs(cDNAs)areproducedfromthesemRNAsby
reversetranscriptase.TheresultingDNAfragmentsarethen
insertedintoasuitablevectorandcloned

---

---

78.Whichofthefollowingenzymeshave
proofreadingfunctioninPCR
[PolymeraseChainReaction]
a)Taqpolymerase
b)PFUPolymerase
c)Thermosthermophilus
d)Thermalflavus(Replinase)
e)T-7polymerase
CorrectAnswer-B:E
Ans.is'b'i.e.,PFUPolymerase;&'e'i.e.,T-7polymerase[Ref
TextbookofPCRbyMikeMcPherson]
TheuseofhighfidelityDNApolymerasesinPCRisessentialfor
reducingtheintroductionofamplificationerrorsinPCRproducts.
SeveralthermostableDNApolymeraseswith3'5'exonuclease-
dependentproofreadingactivityhavebeenintroducedforhigh.
PfuDNApolymeraseDerivedfromPyrococcusfusarious.
PwoDNApolymeraseIsolatedfromPyrococcuswoesei.
KODHiFiDNApolymeraseIsolatedfromThermococcus
Kodakaraensis.
T7DNApolymerase.

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79.EnzymesrequiredformRNAsynthesis
is/are?
a)RNApolymeraseI
b)RNApolymeraseII
c)Primase
d)Topoisomerase
e)Ligase
CorrectAnswer-B
Ans.is'b'i.e.,RNApolymeraseII[RefHerper's30"'/ep.390-
400]
ItcatalyzesthesynthesisofmRNA,smallnuclearRNA(sn-RNA)
andmiRNA.
TheseproductsarecodedbyclassIIgene,i.e.classIIgeneis
transcribedbymRNA.
ClassIIgenedifferfromclassIandIIIinthatoneofitstranscribed
products(mRNA)istranslatedintoprotein.

---

80.WhichDNApolymerasehas/have
proofreadingactivity-
a)DNApolymeraseI
b)DNApolymeraseII
c)DNApolymerasea
d)DNApolymerase
e)DNApolymerasey
CorrectAnswer-A:B:D
Ans.is'a'i.e.,DNApolymeraseI;'b'i.e.,DNApolymeraseII;&
'd'i.e.,DNApolymerase
DNApolymeraseI-possessesthreedifferentcatalytic
activities:?
1. 5'3'exonucleaseactivity,Polymeraseactivity(5'3'
polymeraseactivity),3'5'exonucleaseactivity,
2. DNApolymeraseI:-Helpsingapfillingandsynthesisbetween
okazakifragmentsoflaggingstrand,andreplacesribonucleotidesof
RNAprimerbydeoxyribonucleotides.Ithas(i)3'5'exonuclease
activity,(ii)5'3'exonucleaseactivityand(iii)polymerase(5'3'
polymerase)activity.
3. DNApolymeraseI:-Helpsingapfillingandsynthesisbetween
okazakifragmentsoflaggingstrand,andreplacesribonucleotidesof
RNAprimerbydeoxyribonucleotides.Ithas(i)3'5'exonuclease
activity,(ii)5'3'exonucleaseactivityand(iii)polymerase(5'
3'polymerase)activity.
4. DNApolymeraseII:-Helpsin(i)proofreading(3'?5'exonuclease
activity),and(ii)DNArepair.

---

5. DNApolymeraseIII:-Itisthemainenzymethatsynthesizes
prokaryoteDNA,i.e.,synthesisofleadingandlaggingstrand.Ithas
(i)513'polymerase(orsimplypolymerase)activityforDNA
synthesis,and(ii)3'-->51exonucleaseactivityforproofreading.

---

81.30SribosomeINTERACTSwithall
except?
a)mRNA
b)ATP
c)GTP
d)Initiatingfactor
e)Elongatingfactor
CorrectAnswer-B:E
ANS-'b'i.e.,ATP;&'e'i.e.,Elongatingfactor[RefDineshPurl
Yalep.482,483]
INIATIATIONprocessbeginsbyformationof30Sinitiationcomplex
between30Sribosomalsubunit,mRNAandformylmettRNA.GTP
servesassourceofenergy.Threeinitiationfactors(IF1,IF2,IF3)
arealsorequiredforformationofthiscomplex.
Thenthereisformationof70Sinitiationcomplexbyjoiningof50S
and30Ssubunits.Inthiscomplex,initiatortRNAoccopiesP-siteon
theribosome.`A'-siteisstillempty.
Elongationfactors:EF-Tu,EF-Ts,EF-G.

---

82.Components/genesinvolvedinRISC
complex-
a)Pasha
b)MiRNA
c)rRNA
d)Drosha
e)Dicernuclease
CorrectAnswer-A:B:D:E
Ans.is'a'i.e.,Pasha;'b'i.e.,MiRNA;'d'i.e.,Drosha;&'e'i.e.,
Dicernuclease[RefTextbookofmolecularbiologyp.7121]
RNA-inducedsilencingcomplex(RISC)isamultiproteincomplex
thatincorporatesonestrandofadoublestrandedsmallinterfering
RNA(siRNA)orsinglestrandedmicroRNA(miRNA).
RISCusesthesiRNAormiRNAasatemplateforrecognizing
complementarymRNA.
OnceRISCfindscomplementarystrandofmRNA(withhelpof
miRNAorsiRNA),itactivatesRNAasetocleave(degrade)mRNA.
TheRISC-loadingcomplex(RLC)istheessentialstructurerequired
toloaddsRNAfragmentsintoRISCinordertotargetmRNA.The
RLCconsistsofdicer,thehumanimmunodeficiencyvirus
transactivatingresponseRNA-bindingprotein(TRBP)and
Argonuate2.
AnuclearRNAasespecificfordsRNAcalledDroshaactswitha
nucleards-RNAbindingprotiencalledDGCRinhuman(Pashain
Dorsophila)andcleavesthehairpinregionoutoflongprecursor
RNAgeneratingapre-miRNA.

---

---

83.30SribosomeCONSISTofallexcept-
a)mRNA
b)ATP
c)GTP
d)InitiatingfactorandElongatingfactor
e)None
CorrectAnswer-E
Ans.isNone[RefLippincates5th/ep.436]
Ribosomesarelargecomplexesofr-RNAandproteinswithone
largeandonesmallsubunits.
Thesmallsubunitbindsm-RNA,thusguidinginteractionbetween
m-RNAcodonandanticodonoft-RNAtoreadthegenetic
informationwithexiquisitefidelity.Hencesmallsubunitis
responsibleforaccuracy,whereasthelargesubunitcatalyzes
theformationofpeptidebond.
Ribosomesarecomposedoftwounequalsubunits.
Eukaryotic(80S)ribosomeismadeupof60Sand40Ssubunits.
Prokaryotic(70S)ribosomeismadeof50Sand30Ssubunits.
60Ssubunitofeukaryotescontains5SrRNA,5.8SrRNA,28S
rRNAandmorethan50polypeptides.40Ssubunitcontains18S
rRNAandabout30polypeptidechains.

---

84.Whichofthefollowingisrequiredfor
unwindingofDNA-
a)Helicase
b)Primase
c)SSBP
d)Ligase
e)Topoisomerase
CorrectAnswer-A
Ans.is'a'i.e.,Helicase[Ref:Harper's30thlep.383&29thp.367]
protein
function
DNApolymerases Deoxynucleotidepolymerization
Helicases
ProcessiveunwindingofDNA
Relievetorsionalstrainthatresults
Topoisomerases
fromhelicaseinducedunwinding
DNAprimase
InitiatessynthesisofRNAprimers
Single-strand
Preventprematurereanneallingof
bindingproteins
dsDNA
Sealsthesinglestrandnick
betweenthenascentchainand
DNAligase
Okazakifragmentsonlagging
strand

---

85.Trueaboutcollagen:
a)Doublehelixstructure
b)Singlehelixstructure
c)Triplehelixstructure
d)-pleatedstructure
e)Componentofconnectivetissueofbody
CorrectAnswer-C:E
Ans:c.Triplehelix...,e.Component....[RefHarper30th/46-
47,627-32;Lippincott6th/43-48;Vasudevan5th/254-55]
Incollagen,thecollagenhelix,ortype-2helix,isamajorshapein
secondarystructure
Allcollagenhaveatriplehelicalstructure.
Astrikingcharacteristicofcollagenisoccurrenceofglycineresidue
ateverythirdpositionoftriplehelicalportionofachain.
Thisrepeatingstructure,representedas(Gly-x-y)n,isanabsolute
requirementfortheformationofthetriplehelix.
300nmlongand1.5nmindiameter,itismadeupofthree
polypeptidestrands(calledalphachains),eachpossessingthe
conformationofaleft-handedhelix(itsnameisnottobeconfused
withthecommonlyoccurringalphahelix,aright-handedstructure).
Thesethreeleft-handedhelicesaretwistedtogetherintoaright-
handedcoiledcoil,atriplehelixor"superhelix"
Collagen,themajorcomponentofmostconnectivetissues,
constitutesapproximately25%oftheproteinofmammals.
Itprovidesanextracellularframeworkforallmetazoananimalsand
existsinvirtuallyeveryanimaltissue.Atleast28distincttypesof

---

collagenmadeupofover30distinctpolypeptidechains(each
encodedbyaseparategene)havebeenidentifiedinhumantissues.

---

86.Atisoelectricpoint(p1)netchargeof
aminoacisis:
a)-1
b)+1
c)-2
d)+1
e)0
CorrectAnswer-E
Ans:e.0...[RefHarper30th/201]
Isoelectricpoint(pI)isapHinwhichnetchargeofaminoacidis
zero"(Harper30th/20)
"Isoelectricpoint(pI)isapHinwhichnetchargeofaminoacidis
zero.Incaseofproteinsisoelectricpointmostlydependsonseven
chargedaminoacids:glutamate(6-carboxylgroup),aspartate(13-
carboxylgroup),cysteine(thiolgroup),tyrosine(phenolgroup),
histidine(imidazolesidechains),lysine(c-ammoniumgroup)and
arginine(guanidiniumgroup).

---

87.HexosaminidaseAdeficiencycauses:
a)Niemann-pick
b)Tay-Sachsdisease
c)Hurlersyndrome
d)Gaucher'sdisease
e)Krabbe'sdisease
CorrectAnswer-B
Ans:b.Tay-Sachsdisease[RefsHarper30th/251;Lippincott
6th/212;Harrison19th/432e,433e
HexosaminidaseAdeficiencyisanenzymedeficiencythatcauses
brainandothernervecellstodie,whichcanleadtosevere
neurologicalandmentalproblems.
HexosaminidaseA(HEXA)deficiencyiscausedbyadeficiencyin
anenzymecalledbeta-hexosaminidaseA.Thisenzymehelpsbreak
downaparticularfattyacidcalledGM2ganglioside.
Withoutadequateamountsoffunctionalenzymes,GM2ganglioside
willbuildupinnervecellsandcausethemtodie.
ThereareseveralformsofHEXAdeficiency,includingacute
infantile(Tay-Sachsdisease),juvenile,chronic,oradult-onsetforms.

---

88.Mitchondrialmatrixcontainsenzymesof:
a)Pyruvatedehydrogenase
b)TCAcycleenzyme
c)AcylCoAsynthetase
d)ATPsynthase
e)-oxidationenzymes
CorrectAnswer-A:B:D
Ans:a.Pyruvatedehydrogenase,b.TCAcycleenzyme,d.ATP
synthase
MatrixoftheMitochondrionisgel-likesolutionintheinteriorof
mitochondriais50%protein.Thesemoleculesincludetheenzymes
responsiblefortheoxidationofpyruvate,aminoacids,fattyacids(by
n-oxidation),andthoseofthetricarboxylicacid(TCA)cycle.
Thesynthesisofglucose,urea,andhemeoccurpartiallyinthe
matrixofmitochondria.Inaddition,thematrixcontainsNAD+and
FAD(theoxidizedformsofthetwocoenzymesthatarerequiredas
hydrogenacceptors)andADPandPi,whichareusedtoproduce
ATP.

---

89.Whichofthefollowinggroup(s)are
presentinnaturalaminoacids:
a)Imidazolegroup
b)Tetrapyrrolegroup
c)Indolegroup
d)Guanidiniumgroup
e)Ketogroup
CorrectAnswer-A:B:C:D
Ans:a.Imidazole...,b.Tetrapyrrole...,c.Indole...,d.
Guanidinium(RefHarper30th/20-23;Lippincott6th/I-11;
Vasudevan5th/19]
Imidazolegroup:Histidine,Betacarboxylgroup:Asparticacid
(Vasudevan5th/19)Gammacarboxylgroup:Glutamicacid
(Vasudevan5th/19)?-aminogroup:Lysine(Vasudevan5th/19).
SpecialgroupsinAminoacidsVasudevan5th/17:Benzenegroup-
PhenylalanineIndolegroupin-TryptophanPyrrolidinegroup-
ProlineGuanidiniumgroup-ArgininePhenolgroup-Tyrosine

---

90.Whichofthefollowingvitamindeficiency
causetriadofmentalconfusion,
ophthalmoplegia&ataxia:
a)VitB2
b)VitB1
c)VitB6
d)VitC
e)Vit.B12
CorrectAnswer-B
Ans:b.VitBl[RefLippincott6th/378-79;Harrison19th/96e,
18th/594-96;Harper30th/555-56,28th/468]
Classically,Wernicke'sencephalopathyischaracterizedbythetriad
ofophthalmoplegia,ataxia,andmentalconfusion,butconfusion&a
staggeringgaitareperhapsmostcommon"-SynopsisofPsychaitry
by(Kaplan11th/796-799)
Thiaminedeficiencyinitsearlystageinducesanorexiaand
nonspecificsymptoms(e.g.,irritability,decreaseinshort-term
memory).
Alcoholicpatientswithchronicthiaminedeficiencyalsomayhave
centralnervoussystem(CNS)manifestationsknownasWernicke's
encephalopathy,whichconsistsofhorizontalnystagmus,
ophthalmoplegia(duetoweaknessofoneormoreextraocular
muscles),cerebellarataxia,andmentalimpairment

---

91.Whichofthefollowingenzyme(s)is/are
involvedingluconeogenesis:
a)Pyruvatecarboxylase
b)Phosphoenolpyruvatecarboxykinase
c)Phosphofructokinase-1
d)Glucose6-phosphatase
e)Pyruvatedehydrogenase
CorrectAnswer-A:B:D
Ans:a.Pyruvatecarboxylase,b.Phosphoenolpyruvate
carboxykinase,d.Glucose6-phosphatase,[RefHarper
30th/188;Lippincott6th/117-122;Harper28th/165-68;
Lippincott4th/329J]
glucose-6-phosphatase,fructose-1,6-bisphosphatase,andPEP
carboxykinase/pyruvatecarboxylase.

---

92.Gelusedinelectrophoresisis/are:
a)Agarosegel
b)Polyacrylamideplaingel
c)PolyacrylamideSDS(Sodiumdodecylsulphate)impregnated
Polyacrylamidegel
d)alloftheabove
e)None
CorrectAnswer-D
Ans.d-alloftheabove[www.lonza.com/go/literature/2043;
Shinde7th/7741]
SeparationofRNAinagarosegelsisusedforanumberofdifferent
purposes,includingNorthernblotstomonitorRNAexpression
levels,checkingRNAintegrityandsizeselectionofRNAforcloning
experiments.SeparationofRNAbasedonfragmentlengthrequires
conditionsthataredifferentfromDNAanalysis.
Theseincludesamplepreparation,theuseofsampleandgel
denaturants,electrophoresisbuffers,andvisualization.Thepurpose
oftheexperimentandthesizeoftheRNAbeingseparatedarethe
primarydriversindeterminingwhichdenaturingsystemtouse.
ThemostfrequentlyuseddenaturantsforRNAagarosegel
electrophoresisareformaldehyde,formaldehyde/formamide,and
glyoxalplusDMSO.

---

93.Whichofthefollowingmethod(s)is/are
usedfordetectionofnucleicacid:
a)Northernblotting
b)Southernblotting
c)Westernblotting
d)Microarray
e)ELISA
CorrectAnswer-A:B:D
Ans:a.Northern...,b.Southern"',d'Microarray'
Sample
Technique
GelUsed Purpose
Analysed
Southern
DNA?
Yes
DetectDNAchanges
blot
Northern
RNA?
Yes
MeasuresmRNAamounts&size
blot
Western
Protein?
Yes
Measuresproteinamount
blot
ASO
DNA?
No
DetectsDNAmutations?
RNAor
MeasuresmanymRNAlevelsat
Microarray
No
cDNA
onetime
Proteins?
Detectsproteins(antigens)or
ELISA
or
No
antibodies?
antibodies
Measuresabundance,distribution,
posttranslai.iurimodifications,
Proteomics Proteins?
Yes
functions&
interactionsofcellularproteins

---

interactionsofcellularproteins

---

94.Mucopolysacchidosis,whichisa
lysosomalstoragedisease,occursdueto
abnormalityin:
a)Hydrolaseenzyme
b)Dehydorgenaseenzyme
c)Lipaseenzyme
d)Phosphatase
e)Acetyl-CoAcarboxylase
CorrectAnswer-A
Ans:a.Hydrolaseenzyme[RefHarper30th/638-39,29th/589,
599,600;Lippincott6th/163-64J
Themucopolysaccharidosesarehereditarydiseasescausedbya
deficiencyofanyoneofthelysosomalhydrolasesnormallyinvolved
inthedegradationofheparansulfateand/ordermatansulfate
Theyareprogressivedisorderscharacterizedbyaccumulationof
glycosaminoglycansinvarioustissues,causingarangeof
symptoms,suchasskeletalandextracellularmatrixdeformities,and
mentalretardation.
Childrenwhoarehomozygousforanyoneofthesediseasesare
apparentlynormalatbirth,thengraduallydeteriorate.Insevere
cases,deathoccursinchildhood.
Diagnosisisconfirmedbymeasuringthepatient'scellularlevelof
thelysosomalhydrolases.Bonemarrowandcordbloodtransplants
havebeenusedtotreatHurlerandHuntersyndrome

---

95.Sulphurofcysteinarenotused/utilizedin
bodyforthefollowingprocess/product:
a)Helpinconversionofcyanidetothiocyanate
b)Thiosulphateformation
c)Introductionofsulphuratominmethionine
d)Disulfidebondformationb/wtwoadjacentpeptide
e)None
CorrectAnswer-C
Ans:c.Introductionofsulphuratominmethionine,[RefHarper
30th/301-02,313-14,29th/285-86;Lippincott6th/263-68;Shinde
7th/471-73,578;Vasudevan5th/191;Satyanarayan3rd/361]
TheH2Sderivedfromthecysteinemaybeoxidizedtosulfites&
thiosulfateserfurtheroxidizedtosulfate.
Cysteinetransaminatestoformbetamercaptopyruvicacid&finally
pyruvate.ThebetamercaptopyruvatecantransferStoCNtoform
thiocynate(SCN).
ThesulphurmayberemovedeitherasH2Sorelementalsulphuror
assulfite,Cysteineondecarboxylationgivesbetamercapto
ethanolamine.ThisisusedforsynthesisofcoenzymeA.
Formationofcysteineisbyusingthecarbonskeletoncontributedby
serine&sulphuroriginatingfrommethionine.

---

96.Whichoneofthefollowingstatements
aboutproteinstructureiscorrect:
a)Proteinsconsistingofonepolypeptidecanhavequaternary
structure
b)Theformationofadisulfidebondinaproteinrequiresthatthe
twoparticipatingcysteineresiduesbeadjacenttoeachotherin
theprimarysequenceoftheprotein
c)Thestabilityofquaternarystructureinproteinsismainlyaresult
ofcovalentbondsamongthesubunits
d)Thedenaturationofproteinsalwaysleadstoirreversiblelossof
secondaryandtertiarystructure
e)Theinformationrequiredforthecorrectfoldingofaproteinis
containedinthespecificsequenceofaminoacidsalongthe
polypeptidechain
CorrectAnswer-E
Ans:e.Theinformationrequiredforthecorrect...[RefHarper
3001/36-41,29th/36-40;Lippincott6th/24,13-20]
Thecorrectfoldingofaproteinisguidedbyspecificinteractions
betweenthesidechainsoftheaminoacidresiduesofthe
polypeptidechain
Thetwocysteineresiduesthatreacttoformthedisulfidebondmay
beagreatdistanceapartintheprimarystructure(oronseparate
polypeptides),butarebroughtintocloseproximitybythethree-
dimensionalfoldingofthepolypeptidechain.Denaturationmay
eitherbereversibleorirreversible.
Quaternarystructurerequiresmorethanonepolypeptidechain.

---

Thesechainsassociatethroughnoncovalentinteractions"
Primarystructuresarestabilizedbycovalentpeptidebonds.Higher
ordersofstructurearestabilizedbyweakforces--multiplehydrogen
bonds,salt(electrostatic)bonds,andassociationofhydrophobicR
groups.
Proteindenaturationresultsintheunfoldinganddisorganizationof
theprotein'sstructure,whicharenotaccompaniedbyhydrolysisof
peptidebonds.Denaturationmaybereversibleor,morecommonly,
irreversible.

---

97.Trueaboutretinol:
a)Formpartofrhodopsin
b)Transportedfromintestinetoliverbyviachylomicrons
c)Activelytakepartinvisualcycle
d)Implicatedingrowth&differentiationoftissue
e)Notformedbyretinoicacid
CorrectAnswer-B:D:E
Ans:b.Transportedfromintestinetoliverbyviachylomicrons,
d.Implicatedingrowth&differentiationoftissue,&e.Not
formedbyretinoicacid,
[RefHarper30th/547-51,29th/526-28;Lippincott6th/381-83;
Shinde7th/152-56;Vasudevan5th/284-86]
Retinoicacidisproducedbyoxidationofretinal.However,retinoic
acidcannotgiverisetotheformationofretinalorretinol"
Retinoicacidisimplicatedingrowth&differentiationoftissue,itis
necessaryforthereproductivesystem.Retinol
actslikeasteroidhormoneincontrollingtheexpressionofcertain
genes.ThismayaccountfortherequirementofVitAfornormal
reproduction
Retinylesterspresentinthedietarehydrolyzedintheintestinal
mucosa,releasingretinolandfreefattyacids.Retinolderivedfrom
estersandfromthecleavageandreductionofcarotenesisre-
esterifiedtolong-chainfattyacidsintheintestinalmucosaand
secretedasacomponentofchylomicronsintothelymphaticsystem.
Retinylesterscontainedinchylomicronremnantsaretakenupby,
andstoredin,theliver.
retinolisreleasedfromtheliverandtransportedtoextrahepatic

---

tissuesbytheplasmaretinolbindingprotein(RBP).

---

98.Inprolongfastingglycerolisformedfrom
triglyceride.Whichofthefollowing
statement(s)is/aretrueregarding
glycerol:
a)Usedinsynthesisofchylomicron
b)Itisdirectlyusedbytissuesforenergyneeds
c)Itisformedduetoincreasedactivityoflipoproteinlipase
d)Itisformedduetoincreasedactivityofhormonesensitive
lipase
e)Glycerolactsasasubstrateforgluconeogenesisintheliver
CorrectAnswer-D:E
Ans:d.Itisformedduetoincreasedactivityofhormone
sensitivelipase,&e.Glycerolactsasasubstratefor
gluconeogenesisintheliver,[RefHarper30th/262,149,
29th/160-61;Lippincott6th/331,178,190].
Fasting:Inadiposetissuethedecreaseininsulinandincreasein
glucagonresultsininhibitionoflipogenesis,inactivationof
lipoproteinlipase,andactivationofintracellularhormone-sensitive
lipase.
Thisleadstoreleasefromadiposetissueofincreasedamountsof
glycerol(whichisasubstrateforgluconeogenesisintheliver)and
freefattyacids,whichareusedbyliver,heart,andskeletalmuscle
astheirpreferredmetabolicfuel,thereforesparingglucose.
TheglycerolproducedfromTAGdegradationisusedasa
gluconeogenicprecursorbytheliver.
LipolysisIsControlledbyHormone-SensitiveLipase,whichis

---

?activatedbyACTH,TSH,glucagon,epinephrine,norepinephrine,
andvasopressinandinhibitedbyinsulin,prostaglandinE1and
nicotinicacid
Activityofthehormone-sensitivelipaseisincreasedbyfastingand
stressanddecreasedbyfeedingandinsulin.Conversely,feeding
increasesandfastingandstressdecreasetheactivityoflipoprotein
lipase

---

99.Pyruvatedehydrogenasecomplexuses
followingcoenzymes/cofactors:
a)Biotin
b)Lipoicacid
c)NAD
d)FMN
e)TPP
CorrectAnswer-B:C:E
Ans:b.Lipotic.acid.,c.NAD&e.TPP(RefHarper30th/172-74,
29th/174-75;Lippincott6th/109-11;Satyanarayan3rd/253-54]
PyruvateDehydrogenaseComplex(PDH)Satyanarayan
3rd/253-54
Itisfoundonlyinmitochondria,HighactivityofPDHarefoundin
cardiacmuscle&kidney
TheenzymePDHrequiresfivecofactors(coenzymes)namely-TPP,
lipoamide(itcontainslipoicacidlinkedtoc-aminogroupoflysine),
FAD,coenzymeA&NAD+,PDHisinhibitedbyarsenite
Pyruvatedehydrogenaseirreversiblyconvertspyruvate,theend
productofglycolysis,intoacetylCoA,amajorfuelfortheTCAcycle
andthebuildingblockforfattyacidsynthesis.
ThePDHcomplexcontainsfivecoenzymesthatactascarriersor
oxidantsfortheintermediatesofthereactions.Elrequiresthiamine
pyrophosphate(TPP),E2requireslipoicacidandCoA,andE3
requiresFADandNAD+.

---

100.InconversionofpyruvatetoacetylCoA
&CO2,whichofthefollowingcoenzyme
isused:
a)Biotin
b)Lipoicacid
c)TPP
d)Pyridoxalphosphate
e)Tetrahydrofolate
CorrectAnswer-B:C
Ans:b.Lip...&c.TPP[RefaboveQ;Harper30th/172-74,
29th/174-75;Lippincott6th/109-11;Satyanarayan3rd/253-54]
Pyruvatedehydrogenaseirreversiblyconvertspyruvate,theend
productofglycolysis,intoacetylCoA,amajorfuelfor,theTCA
cycleandthebuildingblockforfattyacidsynthesis".(Lippincott
6th/109-10)

---

101.Trueaboutureacycle:
a)Nitrogenoftheureacomesfromalanine&ammonia
b)UsesATPduringconversionofarginosuccinatetoarginine
c)Onconsumptionofhighamountofprotein,excessofurea
formed
d)Occurmainlyincytoplasm
e)Synthesisofargininosuccinateconsumesenergy
CorrectAnswer-C:D:E
Ans:c.Onconsumptionofhigh...,d.Occurmainlyin
cytoplasm&e.Synthesisofarginosuccinate....[RefHarper
30th/290-96,29th/274-88;Lippincott6th/253-55;Shinde7th/450-
51;Vasudevan5th/180-811]
Inhealthypeople,thenormalbloodureaconcentrationis1040
mg/dl.Higherproteinintakemarginallyincreasesbloodurealevel.
CitrullinePlusaspartateformsargininosuccinate,catalysedby
enzymeArgininosuccinatesynthase.ThereactionrequiresATP.
Cleavageofargininosuccinate,catalyzedbyargininosuccinase,
proceedswithretentionofnitrogeninarginineandreleaseofthe
aspartateskeletonasfumarate(requirenoATP)".
Ureahastwoaminogroups,onederivedfromammonia&other
fromaspartate.Carbonatomissuppliedfromcarbondioxide.

---

102.Gangliosidescontains:
a)Phosphate
b)Galactose
c)Sulphate
d)Serine
e)Sailicacid
CorrectAnswer-B:E
Ans:b.Galactose&e.Sailicacid[RefHarper30th/218,250-51,
29th/146,136,234;Lippincott6th/209;Vasudevan5th/78;
ChatterjeaShinde7th/45,58-61].
Agangliosideisamoleculecomposedofaglycosphingolipidwith
oneormoresialicacidslinkedonthesugarchain.
NeuNAc,anacetylatedderivativeofthecarbohydratesialicacid,
makestheheadgroupsofgangliosidesanionicatpH7,which
distinguishesthemfromglobosides.
Gangliosidesarepresentandconcentratedoncellsurfaces,withthe
twohydrocarbonchainsoftheceramidemoietyembeddedinthe
plasmamembraneandtheoligosaccharideslocatedonthe
extracellularsurface,wheretheypresentpointsofrecognitionfor
extracellularmoleculesorsurfacesofneighboringcells.Theyare
foundpredominantlyinthenervoussystemwheretheyconstitute
6%ofallphospholipids.

---

103.WhichofthefollowingRNAcontains
unusalbases:
a)mRNA
b)rRNA
c)tRNA
d)30SRNA
e)50sRNA
CorrectAnswer-B:C
Ans:c.tRNA[RefHarper30th/pg394.
tRNAmoleculecontainahighpercentageofunusalbases,for
example,dihydrouracilerhaveextensiveintra-chainbasepairing
thatleadstocharacteristicsecondary6.,tertiarystructure"-
Lippincott6th/418.
ThetRNAmoleculescontainahighpercentageofunusualbases
(forexample,dihydrouracil)andhaveextensiveintrachainbase-
pairingthatleadstocharacteristicsecondaryandtertiarystructure.
EachtRNAservesasan"adaptor"moleculethatcarriesitsspecific
aminoacid--covalentlyattachedtoits3'-end--tothesiteofprotein
synthesis.Thereitrecognizesthegeneticcodesequenceonan
mRNA,whichspecifiestheadditionofitsaminoacidtothegrowing
peptidechain

---

104.AllaretrueaboutstructureofDNA
except:
a)Right-handedhelix
b)Left-handedhelix
c)Phosphateformbackbone
d)Deoxyriboseformsbackbone
e)Nitrogenbasesformbackbone
CorrectAnswer-E
Ans:e.Nitroge...[RefHarper30th/359-61,29th/354-60;
Lippincott6th/395-400;Ananthanarayan9th/54)
Eachchainofdoublehelixhasabackboneofdeoxyribose&
phosphateresiduesarrangedalternately.Attachedtoeach
deoxyriboseisoneofthe4nitrogenousbases:A,G,CforT"
Ananthanarayan9th/54
ThecommonformofDNAissaidtoberight-handed.Inthetest
tube,double-strandedDNAcanexistinatleastsixforms(A-E&Z)"
Withtheexceptionofafewvirusesthatcontainsingle-stranded(ss)
DNA,DNAexistsasadoublestranded(ds)molecule,inwhichthe
twostrandswindaroundeachother,formingadoublehelix
TheAformisproducedbymoderatelydehydratingtheBform.Itis
alsoaright-handedhelix,butthereare11basepairsperturn,
andtheplanesofthebasepairsaretilted20"
awayfromtheperpendiculartothehelicalaxis..Z-DNAisa
left-handedhelixthatcontainsabout12basepairsperturn
(Note:deoxyribose-phosphatebackbone"zigzags,"hence,the
name'S"-DNA)

---

---

105.Whichofthefollowingisfalse:
a)RatioofA:T&G:Cisapproximatelyequalto1:1
b)RatioofA:G&T:Cisapproximatelyequalto1:1
c)A+T=G+C
d)A+C=G+T
e)A+G=C+T
CorrectAnswer-B:C
Ans:b.RatioofA:G...&c.A+T=G+C(RefHarper30th/360-61;
Satyanarayan3rd/73;Lippincott4th/291;Ananthanarayan
9th/54-55]
ChargaffrulestatedthatinDNAmoleculestheconcentrationof
deoxyadenosine(A)nucleotidesequalsthatofthymidine(T)
nucleotides(A=T),whiletheconcentrationofdeoxyguanosine(G)
nucleotidesequalsthatofdeoxycytidine(C)nucleotides(G=C)
Thetwostrandsofthisdouble-strandedhelixareheldbyboth,
hydrogenbondsbetweenthepurineandpyrimidinebasesofthe
respectivelinearmoleculesandbyvanderWaalsandhydrophobic
interactionsbetweenthestackedadjacentbasepairs.
Thepairingsbetweenthepurineandpyrimidinenucleotidesonthe
oppositestrandsareveryspecificandaredependentupon
hydrogenbondingofAwithTandGwithC
"Theratioofeachpairofbases(A?T)/(G+C)thoughconstantfor
eachspecies,varieswidelyfromonebacterialspeciestoanother"-
Ananthanarayan9th/54

---

106.Trueaboutrestrictionenzyme:
a)Alsok/arestrictionendonuclease
b)Producestickyends
c)Candetectmutations
d)Obtainedfromvirus
e)Breaksatsugar-phosphatebond
CorrectAnswer-A:B:E
Ans:a.Alsok/a.restriction...,b.Producestickyends&e.
Breaksatsugar-phosphatebond.[RefHarper30th/452-54,
28th/388-90;Lippincott4th/465-66;Satyanarayana3rd/580]
REcanspecificallyrecognizeDNAwithparticularsequenceof4-6
mucleotidesandcleave.Therecognitionsequencesare
palindromicQ(i.e.,twofoldrotationalsymmetry"(Lippincott4th/466)
Itisanenzymethatcleavedouble-strandedDNAQatspecific
recognitionnucleotideknownasrestrictionsitesQ.TocuttheDNA,
arestrictionenzymemakestwoincisions,onethrougheachsugar-
phosphatebackboneQ(i.e.eachstrand)oftheDNAdoublehelix.
Thisenzymecanrestrictviralreplicationsocalledrestriction
enzymes.
ThecutDNAfragmentsbyREmayhavestickyends(cohesive
ends)QorbluntsendsQdependingonthemechanismusedby
enzyme.DNAfragmentswithstickyendsareparticularlyusefulfor
recombinantDNAexperiments(hybridorchimericDNAmolecules).
TocuttheDNA,arestrictionenzymemakestwoincisions,once
througheachsugar-phosphatebackbone(i.e.eachstrand)ofthe
DNAdoublehelix.

---

---

107.GenesinCpPislandisinactivatedby:
a)Methylation
b)Metrylation
c)Ubiquitisation
d)Acetylation
e)None
CorrectAnswer-A
Ans:a.Methylation[RefLippincott6th/709;Harrison19th/101e-
4,18th/668,679;Robbins9th/893;Satyanarayan3rd/359,572;
Lippincott4th/460-62;ChatterjeaShinde7th/346,426;en.
wikipedia.org/wiki/DNA_methylationj
CpGislands:Methylationofcytosinebyamethyltransferaseis
associatedwithsilencingoftheactivitiesofcertaingene"-Lippincott
6th/709
CytosineinthesequenceCGofDNAgetsmethylatedtoform5'-
methylcytosine.AmajorportionofCG(about20%)inhumanDNA
existsinmethylatedform.Ingeneral,methylationleadstolossof
transcriptionalactivity&thusinactivationofgenes.
Theroleofepigeneticcontrolmechanismsinthedevelopmentof
humancancerisunclear.However,ageneraldecreaseinthelevel
ofDNAmethylationhasbeennotedasacommonchangeincancer.
Inaddition,numerousgenes,includingsometumor-suppressor
genes,appeartobecomehypermethylatedandsilencedduring
tumorigenesis.

---

108.Whichofthefollowingis/aretrueabout
PCRexcept:
a)UsesheatlabileDNApolymerase
b)UsesheatstableDNApolymerase
c)IstechniqueforDNAamplification
d)UsedtoyieldmultiplecopiesofDNA
e)Reversetranscriptase-PCRisusedforquantificationofRNA
CorrectAnswer-A
Ans:a.UsesheatlabileDNApolymerase,[RefHarper30th/458-
59;Lippincott6th/479-83,5th/497-83;Chatterjeaer
Shinde7th/267-272]
SpecificityQisbasedontheuseoftwooligonucleotideprimersthat
hybridizetocomplementarysequenceonoppositestrandsofDNA&
flankthetargetsequenceDoublestrandedDNAcanbedisruptedby
heatorhighpH,givingrisetosinglestrandedDNA.Thesingle
strandedDNAservesasatemplateforsynthesisofa
complementarystrandbyreplicatingenzymes,DNApolymerase.
EarlyPCRreactionusedanE.coliDNApolymerasethatwas
destroyedbyeachheatdenaturationcycle.Substitutionofaheat-
stableDNApolymerase(TaqpolymeraseYfromThermusaquaticus,
obviatesthisproblem&hasmadepossibleautomationofthe
reaction,sincethepolymerasereactionscanberunat70?C

---

109.Whichofthefollowingtechniquesare
usedfordetectionofmutation:
a)RT-PCR
b)Microarray
c)Allele-specificoligonucleotide(ASO)
d)Westrenblot
e)DNAsequencing
CorrectAnswer-A:B:C:E
Ans:a.RT-PCR,b.Microarray,c.Allele-specific
oligonucleotide(ASO)&e.DNAsequencing,
[RefLippincott6th/473;Harper30th/470,29th/483-85;Harrison
19th/83e,443-44,18th/508,17th/406;Vasudevan5th/454-56]
Mutationalanalysis:Morediscretesequencealterationsrelyheavily
ontheuseofPCR,whichallowsrapidgene
amplificationandanalysis.Moreover,PCRmakesitpossibleto
performgenetictestingandmutationalanalysiswithsmallamounts
ofDNAextractedfromleukocytesorevenfromsinglecells,buccal
cells,orhairroots.DNAsequencingcanbeperformeddirectlyon
PCRproductsoronfragmentsclonedintoplasmidvectorsamplified
inbacterialhostcells"(Harrison19th/444).
SouthernblottingcandetectDNAmutationssuchastheinsertionor
deletionofnucleotides.
Itcanalsodetectpointmutationsthatcausethelossorgainof
restrictionenzymecleavagesites.Suchmutationscausethepattern
ofbandstodifferfromthoseseenwithanormalgene.
Acomprehensiveapproachtogenome-scalestudiesconsistsof

---

microarrays,orDNAchips.Usedtodeterminethegeneexpression
patternofthousandsofgenessimultaneously.Microarraysallowthe
detectionofvariationsinDNAsequenceandareusedformutational
analysisandgenotyping.

---

110.Whichofthefollowingtechniqueis/are
usedinquantitificationofviralnucleic
acid:
a)MALDI-TOFMS
b)Branched-chainDNA(bDNA)
c)PCR
d)Gas-LiquidChromatography
e)Biochemicalphenotyping
CorrectAnswer-B:C
Ans:(B)Branched-chainDNA(bDNA)&(C)PCR[RefHarper
29th/26;Lippincott6th/482,485;Harrison19th/150e-3-6,183e-1,
194e-3;http://www.researchgate.net/profile/Ivo_Gut/
publication/8597456_DNA_analysis_by_MALDI-TOP]
QuantitativeNAATsareavailableforHIV(PCR),cytomegalovirus
(PCR),hepatitisBvirus(PCR),andhepatitisCvirus(PCRand
TMA).
Branched-chainDNA(bDNA)testingisanalternativetoNAAT
(Nucleicacidamplificationtechniques)forquantitativenucleicacid
testing.Insuchtesting,bDNAattachestoasitedifferentfromthe
target-bindingsequenceoftheoriginalprobe.
Chemiluminescence-labeledoligonucleotidescanthenbindto
multiplerepeatingsequencesonthebDNA.TheamplifiedbDNA
signalisdetectedbychemiluminescence.bDNAassaysforviral
loadofHIV,hepatitisBvirus,andhepatitisCvirushavebeen
approvedbytheFDA.
TheadvantageofbDNA.assaysoverPCRisthatonlyasingle

---

heating/annealingstepisrequiredtohybridizethetarget-binding
probetothetargetsequenceforamplification.

---

111.Whichofthefollowingis/aremost
severe/dangerouschangeingene:
a)Deletion
b)Insertion
c)Mutation
d)Translocation
e)Duplication
CorrectAnswer-A:B
Ans:a.Deletion&b.Insertion-Mostprobably[RefHarper
30th/416-19;Lippincott6th/434;Harrison19th/432-34;Robbins
9th/160-61;Harshmohan7th/2551.
Deletion&Insertioncouldbepossibleanswer(Pleasegothrough
explanationgiven&otherreferencesfordecidingappropriate
answer
FrameshiftMutationsResultfromDeletionorInsertionof
NucleotidesinDNAThatGeneratesAlteredmRNAs
Thedeletionofasinglenucleotidefromthecodingstrandofagene
resultsinanalteredreadingframeinthemRNA.
ifthreenucleotidesoramultipleofthreearedeletedfromacoding
region,thecorrespondingmRNAwhentranslatedwillprovidea
proteinfromwhichismissingthecorrespondingnumberofamino
acids.Becausethereadingframeisatriplet,thereadingphasewill
notbedisturbedforthosecodonsdistaltothedeletion.
If,however,deletionofoneortwonucleotidesoccursjustpriortoor
withinthenormalterminationcodon(nonsensecodon),thereading
ofthenormalterminationsignalisdisturbed.Suchadeletionmight

---

resultinreadingthroughaterminationsignaluntilanothernonsense
codonisencountered.
Insertionsofoneortwoornonmultiplesofthreenucleotidesintoa
generesultinanmRNAinwhichthereadingframeisdistortedupon
translation,andthesameeffectsthatoccurwithdeletionsare
reflectedinthemRNAtranslation.Thismayresultingarbledamino
acidsequencesdistaltotheinsertionandthegenerationofa
nonsensecodonatordistaltotheinsertion,orperhapsreading
throughthenormalterminationcodon

---

112.TruestatementregardingLactate
dehydrogenasedeficiency:
a)Fumaratelevelincreases
b)Exerciseintolerance
c)Musclecrampsmayoccur
d)Itoperatesinanaerobiccondition
e)ItisthekeyenzymeofKrebcycle
CorrectAnswer-B:C:D
Ans:b.Exercise...,c.Muscle...,d.Itoperate...[RefHarper
30th/171,69,28th/149-151;Harrison19th/433e2;Lippincott
4th/103,111;Chatterjea&Shinde7th/313]1
FumarateisconvertedtomalatebyfumaraseenzymeinKrebcycle
(sofumaratelevelincreasesindefectiveenzymefunctioningin
Krebscycle,notinabnormalityofglycolysisi.e.,lactate
dehydrogenasedeficiency,Lactatedehydrogenasecatalyse
conversionofpyruvicacidtolacticacid.
Lactatedehydrogenasedeficiencyisaconditionthataffectshowthe
bodybreaksdownsugartouseasenergyincells,primarilymuscle
cells.
Therearetwotypesofthiscondition:lactatedehydrogenase-A
deficiency(sometimescalledglycogenstoragediseaseXI)and
lactatedehydrogenase-Bdeficiency.
Peoplewithlactatedehydrogenase-Adeficiencyexperiencefatigue,
musclepain,andcrampsduringexercise(exerciseintolerance).

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113.Hyaloronicacidiscomposedof:
a)N-acetylglucosamine
b)N-acetylgalactosamine
c)Glucuronicacid
d)N-acetylneuramicacid
e)Iduronicacid
CorrectAnswer-A:C
Ans:a.N-acetylandc.Glucuronic[RefHarper30th/156,159,
637,640,28th/119,534-39;Lippincott4th/159,163;Chatterjeaer
Shinde7th/38]
CompositionofHyaluronicAcid:Itiscomposedofrepeatingunitsof
N-acetylglucosamine&D-Glucuronicacid.Onhydrolysis,ityields
equimolecularquantitiesofD-Glucosamine,D-Glucuronicacid&
aceticacid.
Hyaluronicacidispresentinbacteriaandiswidelydistributed
amongvariousanimalsandtissues,includingsynovialfluid,the
vitreousbodyoftheeye,cartilage,andlooseconnectivetissues.
Hyaluronicacidisespeciallyhighinconcentrationinembryonic
tissuesandisthoughttoplayanimportantroleinpermittingcell
migrationduringmorphogenesisandwoundrepair.Itsabilityto
attractwaterintotheextracellularmatrixandthereby"loosenitup"
maybeimportantinthisregard.

---

114.ThesizeofMicrosatelliterepeat
sequenceis:
a)<1kb
b)2-6bp
c)1-3kb
d)>3kb
e)5-20bp
CorrectAnswer-B
Ans:b.2-6bp
sequencesof2-5bprepeatedupto50times.Mayoccurat50000-
100000locationsinthegenome"-Harper30th/377-78,28th/404
Short(2-6bp),inherited,tandemrepeatunitsofDNAoccurabout
50,000-100,000timesinthehumangenome.
Becausetheyoccurmorefrequently--andintheviewoftheroutine
applicationofsensitivePCRmethods--theyarereplacingRFLPsas
themarkerlociforvariousgenomesearches.

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115.AllarefeatureofRefsumdiseaseexcept:
a)Deficiencyofa-hydroxylase
b)Defectinpoxidation
c)Accumulationofphytanicacid
d)Peripheralneuropathy
e)Treatedbyremovingphytanicacidprecursorsfromdiet
CorrectAnswer-B
Ans:b.Defectinpoxidation[RefHarper30th/231,614,28th/I91,
493;Lippincott4th/195;Harrison19th/2681,18th/3456,236]
Refsumdiseaseisarareautosomalrecessivedisordercausedbya
deficiencyofa-hydroxylase"(Lippincott4th/195)
"Refsum'sdisease:Alphaoxidationdoesnotoccur.Alphaoxidation
ismainlyusedforfattyacidsthathaveamethylgroupatbeta-
carbon,whichblockbeta-oxidation.Thisprocessoccurmainlyin
endoplasmicreticulum&somealsoinperoxisomes.
Refsum'sdiseaseisarareneurologicdisorderduetoametabolic
defectthatresultsintheaccumulationofphytanicacid,whichis
foundindairyproductsandruminantfatandmeat.Phytanicacidis
thoughttohavepathologicaleffectsonmembranefunction,protein
prenylation,andgeneexpression"(Harper30th/231,28th/191)
Refsumdiseasecanmanifestininfancytoearlyadulthoodwiththe
classictetradof(1)peripheralneuropathy,(2)retinitispigmentosa,
(3)cerebellarataxia,and(4)elevatedCSFproteinconcentration.
Refsumdiseaseisgeneticallyheterogeneousbutautosomal
recessiveinnature.ClassicalRefsumdiseasewithchildhoodor
earlyadultonsetiscausedbymutationsinthegenethatencodes
forphytanoyl-CoAa-hydroxylase(PAHX).

---

Refsumdiseaseistreatedbyremovingphytanic
precursors(phytols:fishoils,dairyproducts,andruminantfats)
fromthediet.

---

116.Groupofallelesthatarecloselylinked
togetheratagenomiclocus&inherited
togetherasaclusteris/are:
a)Idiotype
b)Haplotype
c)Genotype
d)Phenotype
e)None
CorrectAnswer-B
Ans.(B)Haplotype([RefsHarrison19th/435,18th/497,505;
Robbins9th/195,8th/177])
Theentirehumangenomenowcanbedividedintoblocksknownas
haplotypes,whichcontainvaryingnumbersofcontiguoussingle
nucleotidepolymorphismsonthesamechromosomethatarein
linkagedisequilibrium&henceinheritedtogetherasacluster
Ahaplotypereferstoagroupofallelesthatarecloselylinked
togetheratagenomiclocus.
Haplotypesareusefulfortrackingthetransmissionofgenomic
segmentswithinfamiliesandfordetectingevidenceofgenetic
recombination,ifthecrossovereventoccursbetweenthealleles.

---

117.Whichofthefollowingistrueregarding
DNAdouble-strandbreaksrepair
pathway
a)Homologousrecombinationrequirealonghomologous
sequencetoguiderepair
b)Non-homologousend-joiningdoesnotrequirealong
homologoussequencetoguiderepair
c)HomologousrecombinationrepairsDNAbeforethecell
d)Non-homologousend-joiningrepairsDNAbeforethecellenters
mitosis
e)Non-homologousendjoiningisprominentDSBrepair
mechanisminmammals
CorrectAnswer-A:B:C:E
Ans:a.Homologus...,b.Non-homologous...,c.Homologous...,
e.Non-homologous...[RefHarper30th/389-91,
Satyanarayan3rd/532;Robbins9th/430-31,8th/302;http:
www.ncbi.nlm.nih.gov/pubmed/20192759]
Non-homologousendjoining(NHEJ)isthepredominanttypeofDSB
repairinmammaliancells,asopposedtolowereukaryotes.
DSBinDNAaredangerous;Theyresultingeneticrecombination
whichmayleadtochromosomaltranslocation,brokenchromosome
&finallycelldeath;DSBscanberepairedbyhomologous
recombinationornon-homologousendjoining;Homologous
recombinationoccursinyeastswhileinmammals,non-homologous
endjoiningdominates
Double-StrandBreaksRepairMechanism

---

1. Double-strandbreakscanberepairedthroughhomologous
recombinationorthroughnon-homologousendjoining(NHEJ).
2. NHEJisaDNArepairmechanismwhich,unlikehomologous
recombination,doesnotrequirealonghomologoussequenceto
guiderepair.
3. WhetherhomologousrecombinationorNHEJisusedtorepair
double-strandbreaksislargelydeterminedbythephaseofcell
cycle.HomologousrecombinationrepairsDNAbeforethecellenters
mitosis(Mphase).
4. DNAdouble-strandbreaks(DSB)arepresumedtobethemost
deleteriousDNAlesionsastheydisruptbothDNAstrands.
5. Homologousrecombination(HR),single-strandannealing,andnon-
homologousendjoiningareconsideredtobethepathwaysfor
repairingDSB.

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118.Whichofthefollowingenzyme(s)
participateinproteinsynthesis:
a)DNAligase
b)DNAHelicase
c)Peptidase
d)Peptidyltransferase
e)DNApolymerase
CorrectAnswer-D
Ans:d.Peptidyltransferase
[RefHarper30th/422-24,28th/359-66,323;Lippincott4th/438-42;
Chatterjea&Shinde7th/248-501
EnzymeRequiredforTranslation
Amino-acyl-t-RNAsynthetase:Enzymerequiredforactivationof
aminoacids,Peptidesynthetase(peptidyltransferase)
TheNH2ofnewaminoacylt-RNA(AI)in'A'sitecombinewiththe
-COOHgroupofMet-t-RNAoccupyingthe'P'site.Thereactionis
catalyzedbypeptidyltransferase"."Peptidasesdegradesproteinsto
aminoacids
TheNH2ofnewaminoacylt-RNA(AI)in'A'sitecombinewiththe
-COOHgroupofMet-t-RNAoccupyingthe'P'site.Thereactionis
catalyzedbypeptidyltransferase.``peptidasesdegradesproteins
toaminoacids.
Protein
function
DNA
Deoxynucleotide
polymerases
polymerization
Processiveunwindingof
Helicases

---

Helicases
DNA
Relievetorsionalstrain
Topoisomerases thatresultsfromhelicase-
inducedunwinding
InitiatessynthesisofRNA
DNAprimase
primers
Single-strand
Preventpremature
bindingproteins
reannealingofdsDNA
Sealsthesinglestrand
nickbetweenthenascent
DNAligase
Okazakichainand
fragmentsontagging
strand

---

119.Allaretrueregardingepigenetics
mechanismexcept:
a)Non-heritable
b)AcetylationofHistone
c)Hereditary
d)MethylationofDNA
e)Xchromosomeinactivation
CorrectAnswer-A
Ans.(A)Non-heritable
Epigeneticsisdefinedasthestudyofheritablechemical
modificationofDNAorchromatinthatdoesnotaltertheDNA
sequenceitself.Exampleofsuchmodificationincludemethylationof
DNA&themethylationeracetylationofhistones.
Epigeneticmodificationiscriticalfornormaldevelopmentincluding-
regulationoftissuespecificgeneexpression,X-chromosome
inactivation&genomicimprinting.
Anepigeneticmodificationreferstoachangeinthe
genome,heritablebycellprogeny,thatdoesnotinvolveachangein
theDNAsequence.TheinactivationofthesecondXchromosomein
femalecellsisanexampleofanepigeneticsilencingthatprevents
geneexpressionfromtheinactivatedchromosome.

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120.Trueaboutpeptidebondformation:
a)TheNH2groupofnewaminoacylt-RNAatAsitecombinewith
the-COOHgroupofMet-t-RNAoccupyingthe'P'site
b)TheNH2groupofnewaminoacylt-RNAat'P'sitecombine
withthe-COOHgroupofMet-t-RNAoccupyingthe'Asite
c)Reactioniscatalyzedbypeptidyltransferase
d)Peptidebondformationrequireenergy
e)None
CorrectAnswer-A:C
Ans:a.TheNH2andc.Reaction...[RefHarper30th/422-25,
28th/359-66;Lippincott4th/438-42;Chatterjeate?Shinde7th/248-
501]
Thea-aminogroupofthenewaminoacyl-tRNAintheAsitecarries
outanucleophilicattackontheesterifiedcarboxylgroupofthe
peptidyl-tRNAoccupyingthePsite(peptidylorpolypeptidesite).At
initiation,thissiteisoccupiedbyaminoacyl-tRNAmet'.
Thisreactioniscatalyzedbyapeptidyltransferase,acomponent
ofthe28SRNAofthe60Sribosomalsubunit.Thisisanother
exampleofribozymeactivityandindicatesanimportant--and
previouslyunsuspected--directroleforRNAinproteinsynthesis.
Becausetheaminoacidontheaminoacyl-tRNAisalready
"activatornofurtherenergysourceisrequiredforthisreaction.The
reactionresultsinattachmentofthegrowingpeptidechaintothe
tRNAintheAsite.

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121.AllaretrueaboutDNAmethylation
except:
a)Itusuallyoccursinthecytosine
b)Canaltersthegeneexpressionpatternincells
c)Roleingenomicimprinting
d)Noroleincarcinogenesis
e)Essentialfornormaldevelopment
CorrectAnswer-D
Ans:(D)Noroleincarcinogenesis[RefHarper30th/438;
Harrison19th/101e-4,18th/668,679;Robbins9th/319-20,893,
8th/306;Satyanarayan3rd/359,572;Lippincott4th/460-62;
ChatterjeaShinde7th/346,426;en.wikipedia.org/wiki/
DNA_methylation]
CytosineinthesequenceCGofDNAgetsmethylatedtoform5'-
methylcytosine.AmajorportionofCG(about20%)inhumanDNA
existsinmethylatedform.
InDNA,methylationusuallyoccursintheCpGislands,aCGrich
region,upstreamofthepromoterregion.Inhumans,DNA
methylationiscarriedoutbyagroupofenzymescalledDNA
methyltransferases.
DNAmethylationstablyaltersthegeneexpressionpatternincells
suchthatcellscan"rememberwheretheyhavebeen"ordecrease
geneexpression
DNAmethylationisessentialfornormaldevelopmentandis
associatedwithanumberofkeyprocessesincludinggenomic
imprinting,X-chromosomeinactivation,suppressionofrepetitive

---

elements,andcarcinogenesis.
Adenineorcytosinemethylationispartoftherestrictionmodification
systemofmanybacteria,inwhichspecificDNAsequencesare
methylatedperiodicallythroughoutthegenome.
Withinthebacterium,methylationprotectsthehostDNAfrom
cleavagebyitsownrestrictionenzyme.UnmethylatedforeignDNA
isnotprotectedfromcleavage.

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122.AllaretrueregardingUreacycleexcept:
a)Ureaformedfromammonia
b)Ratelimitingenzymeisornithinetranscarbamoylase
c)RequireEnergyexpenditure
d)Malateisbyproductofureacycle
e)Onenitrogenofureacomesfromforaspartate
CorrectAnswer-B:D
Ans:b.Ratelimiting...,d.Malate...[RefHarrison19th/434e3-5,
18th/3216,3219;17th/2472-74;Harper30th/290-96,
28th/243;Shinde7th/450-51;Vasudevan5th/180-81]
Ureahastwoaminogroups,onederivedfromammonia&other
fromaspartate.Carbonatomissuppliedfromcarbondioxide.
Rate-limitingenzyme(pacemakerenzyme)ofUreacycle:
CarbamoylphosphatesynthetaseI(CPSIIisinvolvedinpyrimidine
synthesis)"(Harper28th/245).
Rate-limitingenzymeofGlycogenSynthesis:Glycogensynthase
(nottoohardthere)
Rate-limitingenzymeofGlycogenlysis:Glycogenphophorylase
(phophorylasebreaksphosphatebond,whichmeansactivated
glycogenreleasesalotofenergy)
Rate-limitingenzymeofHMPShunt:Glucose-6Phosphate
dehydrogenase(badtolosethisinRBCs)
Rate-limitingenzymeofdenovopyrimidinesynthesis:Carbamoyl
phosphatesynthaseII(CPSIisinvolvedinureacycle)

---

123.Whichofthefollowingistrueregarding
phenylketonuria:
a)Dietaryphenylalaninerestrictionisusedintreatment
b)OccurduetodeficiencyofPhenyalaninehydroxylaseenzyme
c)Occurduetoincreaseactivityofphenyalaninehydroxylase
enzyme
d)Tyrosinemustbesuppliedindiet
e)Dietshouldcontainhighphenylalaninecontainingfooditems
CorrectAnswer-A:B:D
Ans:a.Dietary...,b.Occur...,d.Tyrosine...[RefHarrison
19th/434e1-3,18th/3217-18;Harper30h/304-306,28th/254;
Lippincott4th/270-72]
InpatientswithPKU,tyrosinecannotbesynthesizedfrom
phenylalanine&therefore,itbecomesanessentialaminoacidthat
mustbesuppliedinthediet
Dietaryphenylalaninerestrictionisusuallyinstitutedifblood
phenylalaninelevelsare>300umol/L(5mg/dL).
Treatmentconsistsofaspecialdietlowinphenylalanineand
supplementedwithtyrosine,sincetyrosinebecomesanessential
aminoacidinphenylalaninehydroxylasedeficiency.
Aboutone-thirdofallpatientswithphenylketonuriaandthemajority
ofthosewithmilderforms(phenylalanine<1200umol/Lat
presentation)showincreasedtolerancetodietaryproteinsand
improvedmetaboliccontrolwhentreatedwithtetrahydrobiopterin(5-
20mg/kgperday),anessentialcofactorofphenylalanine
hydroxylase.Thisdrugshouldbeusedinadditiontodietarytherapy.

---

Pregnancyriskscanbeminimizedbycontinuinglifelong
phenylalanine-restricteddietsandassuringstrictphenylalanine
restriction2monthspriortoconceptionandthroughoutgestation.

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124.TrueaboutDNAhyperchromatism:
a)Itisincreaseofabsorbance
b)Measuredbyabsorbanceat260nm(inaspectrophotometer)
c)ItoccurswhentheDNAduplexisdenatured
d)DoublestrandedDNAismorehyperchromicthanssDNA
e)None
CorrectAnswer-A:B:C
Ans:(A)Itisincreaseofabsorbance(B)Measuredby
absorbanceat260nm(inaspectrophotometer)(C)Itoccurs
whentheDNAduplexisdenatured[RefHarper30th/361,
28th/303;Satyanarayan3rd/78;Lippincott4th/397-98]
Hyperchromicityistheincreaseofabsorbance(opticaldensity)ofa
material.Themostfamousexampleisthehyperchromicityof
DNAthatoccurswhentheDNAduplexisdenatured
Itistheincreaseofabsorbance(opticaldensity)ofamaterial.The
mostfamousexampleisthehyperchromicityofDNAthatoccurs
whentheDNAduplexisdenatured.
'Atawavelengthof260nm,ssDNAhasahigherrelative
absorbancethandoesdoublestrandedDNA"(Lippincott
4th/397-98)
TheUVabsorptionisincreasedwhenthetwosingleDNAstrands
arebeingseparated,eitherbyheatorbyadditionofdenaturantor
byincreasingthepHlevel.
Lossofhelicalstructurecanbemeasuredbyincreasein
absorbanceat260nm(inaspectrophotometer),Theopposite,a
decreaseofabsorbanceiscalledhypochromicity
Renatuartion(reannealing)istheprocessinwhichtheseparated

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complementaryDNAstrandscanformadoublehelix

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125.InBenedicttest,redcolouris/are
producedby:
a)Sucrose
b)Inositol
c)Fructose
d)Lactose
e)Maltose
CorrectAnswer-C:D:E
Ans:c.Fructose,d.Lactose,e.Maltose[RefLippincott4th/84-
85;ChatterjeaFrShinde7th/31;Satyanarayan3rd/16]
Inositolisalsocalledasmusclesugar.Chemicallyitishexahydroxyl
cyclohexane"(ChatterjeadShinde7th/190)
Reducingsugarscanreactwithchromogenicagents(fore.g,
Benedict'sreagentorFehling'ssolutionorBarfoed'stest)causing
thereagenttobereduced&coloured,withanomericcarbonofthe
sugarbecomingoxidized"(Lippincott4th/84;Satyanarayan3rd/16).
InBenedict'stest,reactionofreducingsugarwithBenedict'sreagent
produceredcolourofcuprousoxide.

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126.Truestatementsare:
a)VitaminAindose20,000unitmaybeusedduringlactationto
preventVitAdeficiencytoinfants
b)HighdoseofVitaminCmaycauserenalstone
c)VitaminEreducesriskofatherosclerosis
d)Folicaciddeficiencycausemicrocyticanaemia
e)BananaisarichsourceofVit.B6
CorrectAnswer-A:B:C:E
Ans:a.Vitamina....,b.High...,c.Vitamine...,e.Banana...[Ref
Harrison19th/96e1-7,18th/599;Harper30th/547-62,28th/47178;
Lippincott4th/374]
Vit.Ctoxicity:Oxalatekidneystonesareoftheoreticconcern
becauseascorbicacidismetabolizedtooxalate,butstoneformation
hasnotbeenfrequentlyreported"(CMDT06/1275)"Prophylaxis
againstxerophthalmia:Lactatingmothersshouldbegiven20,000
IUorallyonceatdeliveryorduringthenext2months.Thiswillraise
theconcentrationofvitaminAinthebreastmilk&therefore,helpto
protectthebreastfedinfant"(Khurana5th/466)
"Folicaciddeficiencycausemegaloblasticanaemia(macrocytic)"
(Lippincott4th/374)
"Vit.Ereducestheriskofatherosclerosis"(Vasudevan5th/291)
"Banana:Itisaverygoodsourceofvitamin-B6(pyridoxine),
providesabout28%ofdaily-recommendedallowance.

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127.Thiaminedeficiencycause(s):
a)Glossitis
b)Polyneuropathy
c)Pellagra
d)Angularstomatitis
e)Cardiomegaly
CorrectAnswer-B:E
Ans:b.Polyneuropathy,e.Cardiomegaly[Re(Harrison
19th/96e-3,18th/594-96;Harper30th/555-56,28th/468]
Wetberiberipresentsprimarilywithcardiovascularsymptoms,due
toimpairedmyocardialenergymetabolismanddysautonomia,and
canoccurafter3monthsofathiamine-deficientdiet.Patients
presentwithanenlargedheart,tachycardia,high-outputcongestive
heartfailure,peripheraledema,andperipheralneuritis.
Patientswithdryberiberipresentwithasymmetricperipheral
neuropathyofthemotorandsensorysystemswithdiminished
reflexes.Theneuropathyaffectsthelegsmostmarkedly,andthese
patientshavedifficultyrisingfromasquattingposition.

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128.Thiamineactasco-enzymefor:
a)Transketolase
b)Pyruvatedehydrogenase
c)Alcoholdehydrogenase
d)Transaminase
e)None
CorrectAnswer-A:B
Ans:a.Transketolase,b.Pyruvate...[RefHarper30th/555,
28th/52;Chatterjea&Shinde7th/166-67]
"NAD+(byvitaminB3)actsasacoenzymeforalcohol
dehydrogenase"(ChatterjeaShinde7th/171)
Pyridoxalphosphate(byvitaminpyridoxine,B6)actsascoenzyme
fortransaminaseslikeaminotransferase.
thiaminepyrophosphateactsascoenzymein:Pyruvate
dehydrogenasemn(oxidativedecarboxylation),a-oxoglutararte
dehydrogenasecomplex(oxidativedecarboxylation),transketolase
(transketolationreaction),tryptophanpyrrolase,pyruvate
carboxylase(non-oxidativedecarboxylation).

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129.Terminalproduct(s)ofphenylalanineis:
a)Fumarate
b)AcetylCoA
c)Oxaloacetate
d)Acetoacetate
e)None
CorrectAnswer-A:B:D
Ans:a.Fumarate,b.AcetylCoA&d.Acetoacetate
[RefHarper30th/285,304,29th/269,290;Lippincott6th/263,262;
Satyanarayan3rd/345-47;Vasudevan5th/202-03]
"Thepredominantmetabolismofphenylalanineoccursthrough
tyrosine.Duringthecourseofdegradation,phenylalanine&tyrosine
areconvertedtometabolite,fumarate&acetoacetate,whichcan
serveasprecursorsforthesynthesisofglucose(fumarate-Itisan
intermediateofthecitricacidcycle&canalsoserveasprecursorfor
gluconeogenesis)&fat(acetoacetate-Itisaketonebodyfromwhich
fatcanbesynthesized)".
Phenylalaninehydroxylaseisanenzymethatcatalyzesthe
hydroxylationofthearomaticside-chainofphenylalanineto
generatetyrosine.
Phenylalanineisfirstconvertedtotyrosine.Subsequentreactions
arethoseoftyrosine"(Harper30th/304,29th/288)"Hydroxylationof
phenylalanineproducetyrosine.Metabolismofphenylalanine&
tyrosinemerge,leadingultimatelytotheformationoffumarateer
acetoacetate.phenylalanine&tyrosineare,therefore,both
glucogenicorketogenic.

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130.NADPHisproducedby:
a)Pyruvatedehydrogense
b)Isocitratedehydrogense
c)a-ketoglutarylDehydrogense
d)SuccinateDehydrogense
e)Malatedehydrogense
CorrectAnswer-A:B:C:E
Ans:a.Pyruvate...,b.Isocitrate....c.a-ketoglutaryl...,&e.
Malate...,
[RefHarper30th/169,29th/177;Lippincott6th/109-13,155;Shinde
7th/321]
MethodofATP
Pathway Reactioncatalyzedby
ATP
formation
1.Pyruvate
1.Respiratorychain
5
dehydrogenase
oxidationof2NADH
2.Isocitrate
2.Respiratorychain
5
dehydrogenase
oxidationof2NADH
3.a-Ketoglutarate
3.Respiratorychain
Citric
5
dehydrogenase
oxidationof2NADH
acid
4.Substratelevel
cycle
4.Succinatethiokinase
2
phosphorylation
5.Succinate
5.Respiratorychain
3
dehydrogenase
oxidationof2ADH2
6.Malate
6.Respiratorychain
5
dehydrogenase
oxidationof2NADH

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131.FunctionofmiRNAis/are:
a)Genesilencing
b)Geneactivation
c)Transcriptioninhibition
d)Translationrepression
e)BreakingofmessengerRNA
CorrectAnswer-A:D:E
Ans:a.Gene...,d.Translation...&e.Breaking...[RefHarper
30th/368,29th/351-52;Lippincott6th/459;Vasudevan5th/436]
RNAinterferenceisamechanismofgenesilencingthrough
decreasedexpressionofmRNA,eitherbyrepressionoftranslation
orbyincreaseddegradation.
miRNAbindtomatchingpiecesofmessengerRNA,turnitintoa
doublestrand&keepitfromdoingitsjob.Theprocesseffectively
blockstheproductionofcorrespondingprotein.
miRNAsaretypically21-25nucleotidesinlengthandaregenerated
bynucleolyticprocessingoftheproductsofdistinct
genes/transcriptionunits.miRNAprecursorsaresinglestrandedbut
haveextensiveintramolecularsecondarystructure.

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132.Opticallyinactiveaminoacidis/are:
a)Threonine
b)Thyronine
c)Valine
d)Glycine
e)Serine
CorrectAnswer-D
Ans:d.Glycine[RefVasudevan5th/20;Shinde7th/78]
Aminoacidshavinganasymmetriccarbonatomexhibitoptical
activity.Asymmetryariseswhen4differentgroupsareattachedto
thesamecarbonatom
Glycineisthesimplestaminoacids&hasnoasymmetriccarbon
atom&thereforeshowsnoopticalactivity.Allothersareoptically
active
Themirrorimageformsproducedwithreferencetothealphacarbon
atom,arecalledD&Lisomers
Isoleucineerthreoninehave2opticallyactivecentres&therefore
eachhas4diastereoisomers

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133.cDNAisusedingeneamplificationin
bacteriainsteadofgenomicDNA
because:
a)Easytoreplicatebecauseofsmallsize
b)cDNAlacksintronwhereasthisispresentingenomicDNA
c)Promotorarenotfoundinbacteria
d)Completegenomecannoteasilyreplicatedinbacteria
e)None
CorrectAnswer-A:B:D
Ans:a.Easy...,b.cDNA...&d.Complete[RefHarper30th/455-
56,29th/438-39;Lippincott6th/469-70;Vasudevan5th/449]
BecausecDNAhasnointervening,itcanbeclonedintoan
expressionvectorforthesynthesisofeukaryoticproteinsby
bacteria";"cDNAlacksintrons&thecontrolregionsofthegene,
whereasthesearepresentingenomicDNA"(Lippincott6th/469)
"Bacterialpromotersarerelativelysimple.
cDNAlibrariescontainthoseDNAsequencesthatonlyappearas
processedmessengerRNAmolecules&thesedifferfromonecell
typetoanother.AcDNAlibrarycomprisescomplementaryDNA
copiesofthepopulationofmRNAsinatissue.
cDNAprobesareusedtodetectDNAfragmentsonSouthernblot
transfersandtodetectandquantitateRNAonNorthernblot
transfers

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134.Informing3Dstructureofprotein
followingcomponentshelp:
a)Hydrogenbonds
b)Aminoacidsequence
c)Interactionbetweenaminoacidsidechains
d)Chaperon
e)allofthese
CorrectAnswer-E
Ans:(E)allofthese[RefHarper30th/39-41,29th/36-40;
Vasudevan5th/27;Lippincott6th/18-19,22;Shinde7th/86-88]
The3-dimensionalarrangementofproteinstructureisreferredtoas
tertiarystructure.Thistypeofarrangementensuresstabilityofthe
molecule.Besidesthehydrogenbonds,disulfidebonds,ionic
interactions(electrostaticbonds)&hydrophobicinteractionsalso
contributetothetertiarystructureofprotein.
Theunique3dimensionalstructureofthenativeconformationis
determinedbyitsprimarystructure,thatis,itsaminoacidsequence,
Interactionsb/wtheaminoacidsidechainsguidethefoldingofthe
polypeptidechaintoformsecondary,tertiary&(sometimes)
quaternarystructures,whichcooperateinstabilizingthenative
conformationoftheprotein.
Inaddition,aspecializedgroupofproteinnamedchaperonesis
requiredfortheproperfoldingofmanyspeciesofproteins.

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135.Testusedforproteinis/are:
a)Westernblot
b)Southernblot
c)ELISA
d)CHIPessay
e)Dotblotting
CorrectAnswer-A:C:D
Ans:a.Westernblot,c.ELISAd.CHIPessay
[RefHarper30th/457,29th/439;Lippincott6th/484,473,485;
Satyanarayan3rd/589]
Westernblot-Measuresproteinamount
ELISA-detectsproteins(antigenorantibodies)

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136.Whichofthefollowingdiseaseoccurs
duetoDNAmoleculerepairdefect:
a)Krabe'sdisease
b)Angelmannsyndrome
c)Xerodermapigmentosum
d)Marfansyndrome
e)Ataxiatelangiectasia
CorrectAnswer-C:E
Ans:c.Xeroderma...,e.Ataxia...[RefHarper30th/390,29th/374,
28th/330-333;Lippincott6th/410-13;Harrison18th/496,
17th/395]
Angelmannsyndromeresultsfromgeneticdisorderthatresultsfrom
defectingenethatencodesubiquitin";"Marfansyndrome:Itis
causedbymutationingeneforfibrillin";"Krabbedisease:dueto13
?galactosidaseenzymedeficiency.
XerodermaPigmentosum(XP):Anautosomalrecessivegenetic
disease;morethan10genesareinvolved;Theclinical
syndromeincludesmarkedsensitivitytosunlight(ultraviolet)with
subsequentformationofmultipleskincancersandpremature
death,Theriskofdevelopingskincancerisincreased1000-to
2000-fold.

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137.FullformofLCATis:
a)Lecithincholesterolacyltransferase
b)Lecithincholineacyltransferase
c)Lecithincholesterolalkyltransferase
d)Lecithincholinealcoholtransferase
e)LecithinCoAtransferase
CorrectAnswer-A
Ans:a.Lecithincholesterol...[RefHarper30th/272,29th/242,
256;Lippincott6th/234-36]
PlasmaLCATIsResponsibleforVirtuallyAllPlasmaCholesteryl
EsterinHumans(Harper29th/256).LCATactivityisassociatedwith
HDLcontainingapoA-I.AscholesterolinHDLbecomesesterified,it
createsaconcentrationgradientanddrawsincholesterolfrom
tissuesandfromotherlipoproteins,thusenablingHDLtofunctionin
reversecholesteroltransport.
Thisprotein,associatedwithHDL,isfoundinplasmaofhumansand
manyotherspecies.Itfacilitatestransferofcholesterylesterfrom
HDLtoVLDL,IDL,andLDLinexchangefortriacylglycerol,relieving
productinhibitionofLCATactivityinHDL.

---

138.Whichvitamindeficiencycause
dementia:
a)VitaminA
b)VitaminC
c)VitaminB12
d)VitaminB1
e)Nicotinicacid
CorrectAnswer-C:D:E
Ans:c.Vitamin...,d.Vitamin...&e.Nicotinic...[RefLippincott
6th/379-80;Harrison19th/463]
Niacinornicotinicaciddeficiencycausespellagra.Thesymptomof
pellagraprogressthroughthethreeDs:dermatitis,diarrhea
&dementia"
Niacinpellagra:pigmentedrashofsun-exposedareas,brightred
tongue,diarrhea,apathy,memoryloss,disorientation
FolateMegaloblasticanemia,atrophicglossitis,depression,T
homocysteine
VitaminMegaloblasticanemia,lossofvibratoryandposition
B12sense,abnormalgait,dementia,impotence,lossofbladder
andbowelcontrol,Thomocysteine,Methylmalonicacid
VitaminCScurvy:petechiae,ecchymosis,coiledhairs,inflamed
andbleedinggums,jointeffusion,poorwoundhealing,fatigue
VitaminAXerophthalmia,nightblindness,Bitot'sspots,follicular
hyperkeratosis,impairedembryonicdevelopment,immune
dysfunction

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139.Whichofthefollowingorgancannotuse
ketonebody:
a)Brain
b)RBC
c)Muscle
d)Heart
e)Liver
CorrectAnswer-A:E
Ans:a.Brain,e.Liver[RefHarper30th/150,211-12,29th/161,
211-12;Lippincott6th/196;Vasudevan5th/1451.
Ketonebodiescanbeusedbyextrahepatictissuesuchasskeletal&
cardiacmuscle,intestinalmucosa&renalcortex.Eventhebraincan
useketonebodiestohelpmeetitsenergyneedsifthebloodlevels
risesufficiently.
Theketonebodiesareformedintheliver;buttheyareutilizedby
extrahepatictissues.Theheartmuscle&renalcortexpreferthe
ketonebodiestoglucoseasfuel.Tissuelikeskeletalmuscle&brain
canalsoutilizetheketonebodiesasalternatesourcesofenergy,if
glucoseisnotavailable.

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