SJB Revised 12/4/2013 Page 1 of 6

Biology

DNAReplication:PaperClip Activity

Name Per. _____ Date: ______

Partner: ______
Partner: ______

Learning Target:DNA Structure & Replication

I Can… Create a simulated gene segment of DNA and take the segment through the process of replication.

I Will…

  • Create a simulated primary segment of a gene representing the nucleotide types within the sequence with assigned colored paperclips.
  • Predict and create a complementary strand of DNA using the base pairing rules.
  • Unzip and replicate the DNA gene segment explaining the steps of the process.
  • Infer and predict what may result from creating an alteration in the nucleotide sequence.

QuickReview:

• EachDNAmoleculehasauniquestructurethatmakesitdifferentfromother

DNAmolecules(Remember – A chromosome is condensed DNA and segments of DNA are genes.)

•ThisdifferenceoccursbecausethesequenceofA,T,C,andGvaryfromone moleculeandgene segmenttoanother.

WhatYouNeedtoKnowAboutDNAReplication:

•To“replicate” DNAmeanstoproducean exactcopyofitself.DNAistheonlyknownmolecule thatcandothis regularly – RNA has been known to replicate under laboratory conditions,

•DNAisabletomakeanexactreplicaofitselfbecauseofthebasepairing characteristicsstressedearlier(AwithTandCwithG).

• WhenDNAmakesaduplicatemoleculeofitself,thetwostrandsunwind.

•Afterthetwostrandshavepulledapart,newbases(A,T,C,G)aswellasnew sugarandphosphateunitscomeintoplaceaccordingto thebasepairingrules.

• Acomes inoppositeofT,andCisoppositeofG.

• Whenthisoccurs,twoidenticalDNAmoleculesarecreated.

ActivityOverview:

Youwillbe makingashortsequenceofahumangenethatcontrolsthebody’s productionofthegrowthhormone,whichcausesgrowthduringchildhoodand adolescence.GeneticengineerscallthisgenethehGH(humanGrowthHormone)gene. Thisgeneisactuallymadeof573nucleotidebasepairs.Youwillonlyconstructthefirst tenbasesinthegene.

Forthisactivity,eachpairofstudentswillneedthe following:

14 / Blueclips = Adenine(A) / This activity should take 30 – 40 minutes
14 / Yellowclips =Thymine(T)
9 / Red clips =Cytosine(C)
9 / Greenclips =Guanine(G)

STEPONE: Usethecoloredpaperclipsaccording tothekey aboveandconstructthe primary (top)strandofthehGHaccordingtothediagramofthegenebelow.Linktheten appropriatecoloredclipsforthetopchainshownbelow.

1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10
A / A / G / C / T / T / A / T / G / G

Predict and fill in the complementary nucleotide base for each of the 10 primary nucleotide bases in the empty row following the rules for base pairing.

NoticethatthebottomstrandoftheDNAmoleculeshould followthe“Ruleofcomplimentarily”, whichmeansthatAbondswithT,andCbondswithG.

STEPTWO: Nowconstructthecomplementary (bottom)strandofthehGHgenebylinkingtenmoreclips intoachainaccordingtothepatternabove.Theentiresequenceofthisgeneisknown. YourDNAmodelshouldresemblethefollowing:

Have the teacher check your progress before you continue. Teacher initials: ______

STEPTHREE:Setthetwochainsside-by-sideasshowninthedrawingabovesothat AbondswithT,andCbondswithG.

YounowhaveamodelofthehGHgene(thefirsttenbasesonly.)

Comparethetwochainswitheachotherside-by-sidetoverifythat CbondswithG,and AbondswithT.Whenthisgenereplicatesinthenucleusofacell,thedouble-strand beginstoseparateatoneend.Asitseparates,newnucleotidebasesaremovedinto placebyenzymes,whichformthebeginningoftwonewidenticalmolecules.TheseA,T, C,andGbasesarepresentinthenucleoplasm of the nucleusofeachcell, andcomefromfoodmolecules. Whenthesenewbasesarebroughtintoplace by enzymes and proteins so thattheAbondswithT,andtheCbondswithG.

STEPFOUR:OpenyourhGHDNAmoleculeasshownbelow:

STEPFIVE:Nowusetheotheravailableclipsto createthebeginningoftwonew strands.RememberAwithTandCwithG.Connect theclipsasfollows:

STEPSIX: Continueseparatingthestrandsandbringinappropriatenewbases(clips) tocreatetwocompletenewdouble-strandedhGHgenemolecules.RememberthatA bondsoppositetoT,andCisoppositeofG.Youshouldhavesixclipsleft.Savethem forlater.

Answerthe questionsthatfollow:

1.Examinethetwodouble-strandedDNAmolecules.Aretheyidenticalordifferent inanyway?Fully support and explain your answer.

2.IfyouwereaskedtoreplicateeachofthetwoDNAmoleculesonyourtableto createfouridenticalDNAmolecules,explain the steps you woulduse to accomplish the replication process.

3.YounowhavetwocopiesofasegmentofthehGHgeneonyourtable.During periodsofgrowthandcell division,thechromosomes,whicharemadeupof genes,mustdivide.WhatfeaturesaboutDNAreplication causeseachnewDNA moleculestobe exactlyliketheoriginal?

*CellscandividealongwiththeirDNAinthismannerwithoutanyerrorsfor thousandsofreplications.Onoccasionanerrorcanoccur.Whenthistypeoferror occursinacell it is calleda “mutation”. How would you define what a mutation is?

STEPSEVEN:Todemonstrateagene mutation,placeoneofyourpapercliphGHDNA strandsinfrontofyou.IdentifythesecondnucleotidebasecalledAdenine(A),whichis blue.Tocauseamutation,removethis2ndblueclipandreplaceitwitharedCytosine (C)clip.Youhave justdemonstratedhowamutationoccurs.Thisreplacementusually occurswhentheDNAisreplicating.

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4.WhenthismutatedDNAmoleculereplicates,willtheresultingnewDNAbe similarordifferentfromtheoriginal hGHgene?Explain.

*Thistypeofmutationcanbe causedbyavarietyofcircumstances,including radiation,chemicalexposure,or itcanoccurspontaneouslywithoutknowncause.

5.Drawstructuresofthenewdouble-strandedmutatedgeneyoucreatedbyusing thelettersA,T,C,andGin amannersimilartothatshownearlier.

1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10

*Sincethesequenceofbasesis differentinthismolecule,thegeneticcodeis different.ThisgeneCANNOTdirectthecell to producenormalhumangrowth hormone (The recipe is wrong).

6.Inyourownwords, explainhowmutationscanoccurincellsandhowthismight affectanorganismwiththemutation. Explain what could happen if the mutation occurred in a somatic cell and what could happen if the mutation occurred in a germ cell or during the process of meiosis.

Whenyou havecompletedthisactivity,pleaseseparateall the paperclipsandcount them –you needtohave14 blueand14 yellow,9redand9green.Thenputthemall backintheZiplocbaggie and leave the activity station ready for the next class.