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PCBl 3023l Examl 2l (Latestl 2026/l 2027l Update)l Review|l 100%l Verifiedl Questionsl &l Answersl |l Gradel A
Q:l Describel thel Xenopusl genus
Answer:
Ifl al germl celll failsl tol dividel afterl DNAl replication,l thel doublingl ofl thel genomel mayl bel passedl onl tol gametesl andl eventuallyl tol thel progeny.l Inl thel Xenopusl genus,l Xl tropicalisl hasl al diploidl genomel andl Xl leavisl hasl duplicationl ofl al wholel genomel andl thisl resultedl inl al tetraploidl species
Q:l Thel transpositionl ofl whatl canl mediatel genel rearrangement?l Why?
Answer:
Thel transpositionl ofl eukaryoticl mobilel geneticl elementsl canl mediatel genel rearrangement.l Ifl twol similarl mobilel geneticl elementsl insertl nearl eachl otherl inl al chromosome,l thel transpositionl mechanisml mayl usel thel endsl ofl thel twol differentl elements,l resultingl inl transposoitionl ofl thel entirel segmentl ofl thel chromosomel betweenl thel twol mobilel electrons
Q:l Ifl thel tranposedl segmentl includesl anl exon,l itsl insertionl intol al secondl genel wouldl createl al newl versionl ofl thatl gene.l Thisl isl anl examplel ofl what?
Answer:
Exonl transposition
Q:l Thel transpositionl ofl eukaryoticl mobilel geneticl elementsl canl alterl regulatoryl sequences.l Whatl isl thel impactl ofl this?
Answer: 1 / 4
Thel rearrangementl ofl regulatoryl sequencesl canl alterl thel tissue-specificl patternl ofl genel expression
Q:l Whatl causesl somel insectsl tol havel legsl onl theirl headl insteadl ofl antennae?
Answer:
Alterationl ofl regulatoryl sequencesl ofl thel Antennapedial genel causedl byl insertionl ofl al mobilel geneticl elementl causesl thel genel tol bel ectopicallyl expressedl inl thel head.l Asl al result,l antennael arel transformedl intol legs.l Thisl isl calledl homeoticl transformation,l whichl isl whenl onel bodyl partl isl replacedl byl anotherl bodyl partl normallyl foundl inl anotherl region
Q:l Whatl isl anl examplel ofl al geneticl changel thatl contributesl tol genel alterationl andl genomel evolution?
Answer:
Conjugation:l thel transferl ofl DNAl froml onl bacteriuml tol another;l virall infections
Q:l Whatl isl conjugationl andl whatl isl thel result?
Answer:
Conjugationl isl thel transferl ofl geneticl information,l vial al plasmid,l froml onel celll tol anotherl throughl al sexl pilus.l Thel resultl isl geneticl recombinationl withoutl reproduction
Q:l Describel thel lipidl bilayer
Answer:
Thel lipidl bilayerl servesl asl al permeabilityl barrierl tol mostl water-solublel molecules,l whilel thel proteinsl embeddedl carryl outl otherl functionsl andl givel thel membranel itsl individuall characteristics.l Thel lipidl bilayerl isl thel basisl ofl alll biologicall membranesl andl itl formsl spontaneouslyl whenl membranel lipidsl arel placedl inl water.l Itl isl composedl ofl phospholipidsl andl proteinl molecules
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Q:l Whatl isl thel plasmal membrane?
Answer:
Twol polysheetsl ofl lipidl moleculesl inl whichl proteinsl havel beenl inserted.l Itl servesl asl al selectivel barrier.l Itl isl alsol involvedl inl celll communication,l import/exportl ofl moleculesml celll growthl andl motility,l andl energyl generation
Q:l Describel thel fluidl mosaicl biologicall membrane.
Answer:
Inl thel fluidl mosaicl biologicall membrane,l lipidsl andl proteinsl diffusel laterallyl withinl thel lipidl layer.l Thel flexibilityl ofl thel membranel andl itsl capacityl forl expansionsl allowl thel celll tol grow,l changel shape,l andl move.l Asl thel celll grows,l sol doesl thel membrane,l andl itl doesl sol withoutl everl losingl continuity.l Thel membranel isl self-healing.l Fluidityl dependsl onl phospholipidl composition,l inl particular,l thel naturel ofl thel hydorphobicl tails:l thel closerl andl morel regularthel packingl ofl thel tails,l thel morel viscousl andl lessl fluid.l Al shorterl taill reducesl interactionsl betweenl tailsl andl resultsl inl morel fluid.l Saturationl (nol doublel bonds)l alsol leadsl tol morel fluidity
Q:l Howl canl phospholipidsl move?
Answer:
Laterall diffusionl (proteinsl canl alsol movel thisl way),l flip-flopl (rarelyl occurs,l onlyl asl anl activel process),l flexion,l orl rotation
Q:l Whatl isl cholesterol'sl purposel inl thel membrane?
Answer:
Cholesteroll isl foundl inl animall celll membranesl (amphipatic)l andl regulatesl thel fluidityl ofl thel membrane.l Duel tol thel shortl andl rigidl steroidl ring,l itl canl filll thel spacesl betweenl neighbouringl phospholipidl moleculesl leftl byl kinksl inl thel unsaturatedl tail.l Thel polarl headl groupl isl -OHl andl thel nonpolarl groupsl arel thel steroidl ringl structurel andl thel hydrocarbonl taill Cholesteroll willl NOTl formal lipidl bilayerl byl itself,l andl itl insteadl insertsl intol pre-formedl lipidl bilayersl tol modulatel membranel fluidityl andl servel asl al temperaturel buffer. 3 / 4
Q:l Howl doesl cholesteroll servel asl al temperaturel buffer?
Answer:
Atl highl temperatures,l cholesteroll preventsl fluidityl byl restrainingl thel movementl ofl fattyl acidsl andl maintainingl stability.l Atl lowl temperatures,l cholesteroll preventsl tightl packingl ofl fattyl acids,l maintainingl fluidity
Q:l Somel lipidl componentsl arel distributedl asymmetricallyl inl thel plasmal membranel bilayer.l Describel thesel components.
Answer:
Glycolipids,l whichl arel sugarsl attachedl tol geads,l arel alwaysl inl thel outerl layerl ofl thel celll membrane.l Theyl arel celll identityl markers,l representl sugars,l andl arel foundl xclusivelyl inl thel nonctyosolicl monolayer Chargedl phospholipidsl arel alwaysl inl thel innerl layerl ofl thel membrane.
Q:l Whatl isl eachl proteinl componentl ofl thel celll membranel andl whatl purposel doesl eachl serve?
Answer:
Transportersl arel carrierl proteinsl andl ionl channels
Anchorsl forl extracellularl matricl and/orl cytoskeletall proteins,l suchl asl integrins
Surfacel receptors,l suchl asl hormonel receptors
Enzymaticl proteinsl likel tyrosinel kinases
Glycoproteinsl andl proteoglycans:
1)l protectivel carbohydratel layerl (alongl withl glycolipids) 2)l celll identityl markers
Q:l Whatl arel peripherall proteinsl andl howl arel theyl differentl froml integrall proteins?
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