Download Student Worksheet Hands-on Activity Viral DNA Integration

Hands-on Activity
Viral DNA Integration
Student Worksheet
INTRODUCTION
Thehumanimmunodeficiencyvirus(HIV)infectsanddestroyscellsoftheimmunesystemcalledhelper
Tcells.Overtime,HIVinfectionweakensaperson’sabilitytofightotherinfectionsandsomediseases.
TheadvancedstageofHIVinfectionistermedacquiredimmunodeficiencysyndrome(AIDS).An
individualwithAIDShasaseverelyimpairedimmunesystem.AlthoughthereisnocureforAIDS,HIV
infectioncanbecontrolledwithpropertreatmentandearlymedicalcare.
HIVisaretrovirus.Likeallviruses,retrovirusescanonlyreplicatewithinhostcells.Theyusethehost
cell’smachinerytomakecopiesoftheviralgenomeandproduceitsproteins.Retrovirusesare
distinguishedfromothertypesofvirusesbytwokeystepsinthereplicationcycle:reversetranscription
andintegration.AfterHIVinfectsahostcell,reversetranscriptionresultsintheproductionofadoublestrandedDNAcopyofthesingle-strandedHIVRNAgenome.Integrationthenresultsintheinsertionof
thedouble-strandedDNAcopyintothehost’sgenome.ThehostcellthentreatstheintegratedHIVDNA
aspartofitsowngenome.
Inthisactivity,youwillmodeltheintegrationprocess.
MATERIALS
Forthisactivity,youwillneedpopbeadsofthreedifferentcolorstorepresent:
•
thedouble-strandedDNAgenomeofthehostcell(about40to50beads)
•
thesingle-strandedRNAgenomeofthevirus(about5to10beads)
•
thedouble-strandedDNAcopyofthevirus’sgenome(doublethenumberofbeadsusedforthe
RNA)
PROCEDURE
1.WatchananimationoftheHIVlifecycle(http://www.hhmi.org/biointeractive/hiv-life-cycle).Pay
particularattentiontothesectiononreversetranscriptionandintegration.Takenotesontheenzymes
involvedinthesetwosteps.YoumayhavenoticedintheanimationthateachHIVparticlecontainstwo
copiesoftheHIVgenome.Eachcopyisasingle-strandedRNAmolecule.
2.GothroughtheHHMI“Click&Learn”activityentitled“VirusExplorer”
(https://www.hhmi.org/biointeractive/virus-explorer).Inparticular,readthedefinitionsforgenome,
structure,andenvelopebyclickingonthe“i”iconnexttoeachword.ClickonHIVandlookatboththe
3-Dmodelandcross-sectionimages.Thenanswerquestions#1-5below.
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February3,2017
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Hands-on Activity
Viral DNA Integration
Student Worksheet
QUESTIONS
1.DrawadiagramandexplainthebasiccharacteristicsofHIV.(Ifyouarefillingouttheformonyour
computer,takeaphotoofyourdrawinganduploaditinthespaceprovided.)
LabeledDiagram
ExplanationofLabeledStructures
2.Definetheterm“genome”anddescribetheHIVgenome.
3.WhatisthehostcellforHIV?Howarethecompositionandsizeofthehostcellgenomedifferent
fromthoseofHIV?
4.Whatistheenzymeresponsibleforreversetranscription?Isitaviralorhostenzyme?
5.WhatistheenzymeresponsiblefortheinsertionoftheviralDNAintothehostgenome?Isitaviralor
hostenzyme?
PROCEDURE
6.Youwillnowmakeamodelofthehostcellgenomeandvirusgenomeusingpopbeads.Usethe
longerstrandtorepresenttheDNAofthehostcell.DrawadiagramofwhatyouconstructedinTable1
below.
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February3,2017
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Hands-on Activity
Viral DNA Integration
Student Worksheet
7.Onceinsidethehostcell,anHIVenzymeproducesadouble-strandedDNAcopyoftheviralgenome.
Usethethirdcolorofpopbeadstomodelthedouble-strandedDNAcopyoftheviralRNA.Drawa
diagramofyourpop-beadmodelinthetablebelow.(Youcanalsotakephotosofyourmodelsand
uploadthephotosinthespacesprovided.)
Table1.ModelsofHostCellGenome,HIVGenome,andReverse-TranscribedViralDNA.
Model
Drawa
diagramofthe
modelyou
constructed
HostCellGenome
HIVgenome
DNAcopyofHIVgenome
Characteristics
(RNAorDNA;
single-or
doublestranded;
relativesize)
8.Comparethethreemoleculesyouconstructed.Whatarethekeysimilaritiesanddifferences?
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February3,2017
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Hands-on Activity
Viral DNA Integration
Student Worksheet
9.AftertheviralDNAisproduced,thenextstepintheHIVlifecycleistheinsertionofviralDNAintothe
hostcellgenome.Usethedouble-strandedviralDNAandthehostDNApop-beadmodelstoconstructa
modelshowinghowthevirus’sgenomeisintegratedintothehostgenome.Drawadiagramofyour
pop-beadconstructionbelowandmakesureyoulabelyourdiagram.(Youcanalsotakeaphotoofyour
modelanduploaditinthespaceprovided.)
10.Describethestepsinvolvedintheintegrationprocess.(Thinkaboutwhatyouhadtodowiththe
beads.)
11.DescribewhathappenstotheviralDNAnowthatitisintegratedintothehostcellgenome.
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