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S-75.160314
S-75Edvo-Kit #S-75
Do Onions, Strawberries and Bananas Have DNA?Experiment Objective:
In this experiment, students will learn about the physical nature of DNA by isolating DNA from onions and using the common procedure of DNA spooling.
See page 3 for storage instructions.
Page
Experiment Components 3
Experiment Requirements 3
Background Information 4
Experiment Procedures Experiment Overview 6 Activity One - Spooling DNA from Solution 7 Activity Two - Staining the Spooled DNA 8 Activity Three - Extraction of DNA from Onion Tissue 9 Activity Four - Extraction of DNA from Strawberries or Banana 10 Study Questions 11
Instructor's Guidelines 12 Pre-Lab Preparations 12 Study Questions and Answers 13
Safety Data Sheets can be found on our website: www.edvotek.com/safety-data-sheets
Table of Contents
Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
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Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
Experiment Components
EDVOTEK and The Biotechnology Education Company are registered trademarks of EDVOTEK, Inc.
Contents Check (√) • DNAExtractionBuffer q• DNAsampleinacappedtesttube q• Transferpipets q• ColoredBeads(4colors) q• Graduatedtesttubes q• Spoolingrods q• Saltpacket q
Experiment #S-75 is designed for 10 groups.
Storage: Store entire experiment
in the refrigerator.
• Freshonionpieces(scallions,alsocalledgreenonions,arehighlyrecommended)• Ripenedfreshstrawberryorbananapieces• 20mlbeaker• Testtubes(13x100mm)• 70%clearisopropylalcohol(rubbingalcohol)• Distilledwater• Ice
All experiment components are intended for educational research only. They are not to be used for diagnostic or drug purposes, nor administered to or consumed by humans or animals.
Requirements
Do Onions, Strawberries and Bananas Have DNA?EDVO-Kit #S-75
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Do Onions, Strawberries and Bananas Have DNA?EDVO-Kit #S-75
Background Information
DNA - DEOXYRIBONUCLEASE
Sincethe1800s,ithasbeenknownthatalllivingorganismsarecomposedofcells.Organismssuchas bacteriaaresinglecells,whileverycomplexorganisms,suchashumans,arecomposedofbillionsofmanydiffer-entcells.
In1868,aSwissbiologistnamedFriedrichMeischercarriedoutresearchwhichindicatedthatthenucleusofcellscontainsamaterialwhichhecallednucleicacid.But,itwasn’tuntilmuchlaterinthe1940’sthatthenucleicacid,deoxyribonucleicacid(DNA),wasrecognizedasthecarrierofgeneticinformation.
DNAplaysanimportantroleintwoprocesses.Duringtheprocessofreplication,DNAprovidesinformationtocopyitself,sogeneticinformationcanbepassedonfromgenerationtogenerationofcells.Initssecondimportantrole,DNAprovidesinstructionsformakingproteins,whicharevi-taltothemaintenanceandfunctionofcells.DNAprovidesinformation for the order of amino acids required for mak-ingvariousproteins.
The structure of the DNA molecule was determined by JamesWatsonandFrancisCrickin1953.TheydeterminedthatDNAwasadoublehelixconsistingoftwostrands.The Watson and Crick model is often described as a spiral ladder.ThetwostrandsofDNAarethebackboneoftheladder,madeofsugarphosphodiestergroups.Thesugarbackboneactsasasupportfortherungsoftheladder.TheserungsarecomposedofthechemicalbasesAdenine,Guanine,Cytosine,andThymine.Thefirstlettersofthesebases,A,G,C,andT,areusedbyscientiststodesignatetheorderofthebaseswithintheDNAstrands.
Thebasesarealwaysarrangedinpairs.WhenAoccursononestrand,Toccursontheoppositestrand. Similarly,GandCareoppositeDNAstrands.Thebasesareheld together by weak bonds which are shown as dashed linesinFigure1.
Figure 1: Structure of DNA
TA
GC
T A
GC
CG
AT
5' 3'
5'3'
CG
Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
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Duplication of any part of this document is permitted for non-profit educational purposes only. Copyright © 1989-2016 EDVOTEK, Inc., all rights reserved. S-75.160314
Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
Background Information
Figure 2: Extracting DNA
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2
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1. The DNA is inside the cell. 2. The cell wall is disrupted.3. The DNA is spooled onto a rod.
DNAcanbeextractedfromthenucleusofcellsbyaddinganaqueousbufferedextractionsolutiontocells.Thecellsarechemicallylysed(brokenopen)andDNAfromchromosomesisreleased.Thisprocedureisknownascelllysis.DNAissolubleinwaterandcannotbeseen,butitisinsolubleinalcohol.Purificationproceduresfornucleicacidsusuallyincludeprecipitationwithalcoholinthepresenceofsalt.Sincerubbingalcohol(isopropylalcohol)hasalowerdensitythanwater,itwillformasecondlayerabovetheDNAsolution.AspoolingrodisusedtospoolthetwoliquidsattheinterfaceofthetwophasestoseparatetheDNAfromthesolution.TheDNAwillappearasaviscous,clottedmassasitiscollectedonthespoolingrod(Figure2).TheamountofDNAspooledisaconse-quenceofthesizeoftheDNAfragmentswhicharemuchlargerthanthesmallbio-moleculessuchasaminoacidsandsmallcarbohydratesugars.
Inthisexperiment,DNAwillbeisolatedinoneoftwoways:1)DNAwillbespooledfromabuffersolution containingsalts;2)DNAwillbeextractedfromtissuessuchasonion,banana,orstrawberryandspooledfrom solution.DNAwillbeobservedbythenakedeyeonthespoolingrod.
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Do Onions, Strawberries and Bananas Have DNA?EDVO-Kit #S-75
EXPERIMENT OBJECTIVE:
Inthisexperiment,studentswilllearnaboutthephysicalnatureofDNAbyisolatingDNAfromonionsandusingthecommonprocedureofDNAspooling.
LABORATORY SAFETY
1. Glovesandgogglesshouldbewornroutinelyasgoodlaboratorypractice.2. Exerciseextremecautionwhenworkingwithequipmentthatisusedinconjunction
withtheheatingand/ormeltingofreagents.3. DONOTMOUTHPIPETREAGENTS-USEPIPETPUMPS. 4. Exercisecautionwhenusinganyelectricalequipmentinthelaboratory.5. Alwayswashhandsthoroughlywithsoapandwaterafterhandlingreagentsorbio-
logicalmaterialsinthelaboratory.
WORKING HYPOTHESIS
DNAcanbeextractedfromthecells,andisolatedfromsolutionbyspooling.
LABORATORY NOTEBOOKS:
Scientistsdocumenteverythingthathappensduringanexperiment,includingexperimentalconditions,thoughtsandobservationswhileconductingtheexperiment,and,ofcourse,anydatacollected.Today,you’llbedocument-ingyourexperimentinalaboratorynotebookoronaseparateworksheet.
Before starting the Experiment: • Carefullyreadtheintroductionandtheprotocol.Usethisinformationtoformahypothesisforthisexperi-
ment. • Predicttheresultsofyourexperiment.
During the Experiment: • Recordyourobservations.
After the Experiment: • Interprettheresults–doesyourdatasupportorcontradictyourhypothesis? • Ifyourepeatedthisexperiment,whatwouldyouchange?Reviseyourhypothesistoreflectthischange.
Experiment Overview
Wear gloves and safety goggles
Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
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Duplication of any part of this document is permitted for non-profit educational purposes only. Copyright © 1989-2016 EDVOTEK, Inc., all rights reserved. S-75.160314
Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
Activity One - Construction DNA Models
THE EXPERIMENT PROCEDURE
1. Eachgroupofstudentswillgetasetofbeadsofvariouscolors.
2. Theteacherwillassignabasedesignationforfourofthecolors.Forexample:
Red = Adenine(A) Blue = Thymine(T) Green = Guanine(G) Yellow = Cytosine(C)
3. Sortallthebeadsbycolor.Baseduponthebeadsyoureceived,correctlyputthecoloredbeadstogetherintwo separate strands to form one or more of the following base pair models:
A-T base pair G-C base pair
HowmanyA-TorG-Cbasepairswereyouabletoputtogether?
PUTTING ALL THE STUDENT BASE PAIR MODELS TOGETHER:
4. Withthehelpofyourteacher,andtherestoftheclass,buildamodeloftheDNAladder.Attachtheendsofseveralbeadsectionstogethertoformtwolongstrandsofdouble-strandedDNA.
7. Inyourownwords,describethestructureofDNA.
Do Onions, Strawberries and Bananas Have DNA?EDVO-Kit #S-75
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Do Onions, Strawberries and Bananas Have DNA?EDVO-Kit #S-75
Activity Two - Teacher Demonstration of DNA Spooling
Inthisactivity,DNAwillbespooledfromanaqueousbufferedsolutionbyaddingsaltandoverlayingwithisopropylalcohol.Theisopropylalcohol(clearrubbingalcohol)shouldbeicecold(storedinafreezeratleast2hoursbeforeuse).Justbeforethedemonstration,placetheDNAsolutionandthealcoholonice.
THE CONTROL
1.Addtwopinchesofsalttoasmallbeakerorcleargraduatedtesttube.
2.Adddistilledwateruptothe2mllevelofthetubeandswirltodissolvethesalt.
3.Useatransferpipettoadd1mlofthecontrolsolution(distilledwater).Swirltomix.
4.Usingatransferpipet,carefullyoverlaythecontrolsolutionwithtwovolumesofverycold 70%clearisopropylalcohol(about6ml).Letthecoldalcoholgentlyflowdownthesideof thebeakerortesttube.Donotmixthetwosolutions.
5. Placetheendofthespoolingrodjustbelowthelineseparatingthetwo solutions(theinterface).Twirltherodwithtwofingersandspool.
6. Recordyourobservationsforthecontrol.
7. Rinsetherodwithdistilledwaterandthoroughlydrywithapapertowel.
THE EXPERIMENT
8. Addtwopinchesofsalttoasmallbeakerorcleargraduatedtesttube.
9. Useatransferpipettoadd2mlofdistilledwaterandswirltodissolvethesalt. 10. UseatransferpipettotransferalloftheDNAsolutiontothesaltwater.Stirorswirltomix.Thetotalvolume
shouldbeapproximately3ml.
11. LayerthecoldalcoholontopoftheDNAsolutioninthesamemannerasstep#4oftheexperiment.Donotmixthetwosolutions.
12. Placetheendofthespoolingrodjustbelowthelineseparatingthetwosolutions(theinterface).TwirltherodwithtwofingersandspooltheDNAfromthesolution.
13. ObservetheDNAandrecordyourobservations.
Wear gloves and safety goggles
FREEZER
- - - - -
Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
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Duplication of any part of this document is permitted for non-profit educational purposes only. Copyright © 1989-2016 EDVOTEK, Inc., all rights reserved. S-75.160314
Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
Activity Three - Extraction of DNA from Onion Tissue
Inthisactivity,DNAisextractedfromoniontissueusinganextractionbufferandspooledfromsolutionbyoverlay-ingtheliquidwithicecoldisopropylalcohol.
THE EXPERIMENT
1. Carefullyslicea5x5x5mmcube(aboutthesizeofapencileraser)fromthemainbodyoftheonion(nottheroottip),andplaceitinoneofthetesttubesprovided.
2. Usingatransferpipet,addDNAExtractionBufferuntilitreachesthe3mllevelmarkonthetube.Mincetheonioncubewiththetipofaspoolingrod,pencilorpen(mashtheonionverywell).ThiswillreleasethecellularcontentsandtheDNAintheonioncells.
3. Withatransferpipet,carefullyremove2mloftheliquidlayerfromthetesttubeandtransferitintoasecond,cleantesttube.Trytominimizecarry-overoftheoniontissue.
4. Carefullyoverlaytheliquidwith4mlofvery cold70%clearIsopropylalcohol.
5. Placeaspoolingrodintothetesttubeandtwirlitwithtwoofyourfingers.Gentlyrotatetherodattheinterfaceofthetwophases.TheDNAwillbegintospool(wrap)aroundtherod.
Gently lift the rod out of the solution from time to time and observe the DNA sub-stanceattachedtoit.
6. Afterspoolingforseveralminutes,removetherodfromthetesttubeto observetheDNA.TheDNAwillappearasaviscousmaterialadheringtothe splint(itmaybegrayishincolorifapencilwasusedtomincetheoniontissue).
7. RecordyourobservationsoftheonionDNA.
THE CONTROL
8. Baseduponwhatyouhavepreviouslylearned,outlineandperformthecontrolforthisactivity.
Do Onions, Strawberries and Bananas Have DNA?EDVO-Kit #S-75
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Do Onions, Strawberries and Bananas Have DNA?EDVO-Kit #S-75
Activity Four - Extraction of DNA from Strawberries or Banana
Inthisactivity,DNAisextractedfromabananaorstrawberriesinthesamemannerastheextractionofDNAfromonion.
1. Carefullyslicea5x5x5mmcubefromthefleshybodyofthebanana orstrawberry,andplaceitinacleantesttube.
2. Usingatransferpipet,addDNAExtractionBufferuntilitreachesthe 3mlmarkonthetube.Mincethecubewiththetipofa spoolingrod,pencilorpentoreleasethecellularcontents.
3. Withatransferpipet,carefullyremove2mloftheliquidlayerfromthetesttubeandtransferitintoasecond,cleantesttube.Trytominimizecarry-overofthebananaorstrawberrytissue.
4. Carefullyoverlaytheliquidwith4mlofvery cold70%clearIsopropylalcohol.
5. Placeaspoolingrodintothetesttubeandtwirlitwithtwoofyourfingers.Gentlyrotatetherodatthe interfaceofthetwophases.TheDNAwillbegintospool(wrap)aroundtherod.
GentlylifttherodoutofthesolutionfromtimetotimeandobservetheDNAsubstanceattachedtoit.
6. Afterspoolingforseveralminutes,removetherodfromthetesttubetoobservetheDNA.TheDNAwill appearasaviscousmaterialadheringtothesplint(itmaybegrayishincolorifapencilwasusedtomince theoniontissue).
7. RecordyourobservationsofthebananaorstrawberryDNA.
Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
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Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
Study Questions
1. DescribetheappearanceoftheisolatedDNA.
2. Whatisanucleus?
3. Whatarenucleotides?
4. Whatarechromosomes?
5. Whatdoescelllysismean?
6. WhydidthealcohollayerontopoftheDNAsolution?
7. WhywasitimportantnottomixthealcoholandDNAsolutions?
8. WhatpropertiesofDNAallowspooling?
9. Whatdifficultiesdidyouhaveinspooling?Why?
10. Howmanychromosomesdohumanshave?
Do Onions, Strawberries and Bananas Have DNA?EDVO-Kit #S-75
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Do Onions, Strawberries and Bananas Have DNA?EDVO-Kit #S-75
Instructor's Guide
Pre-Lab Preparations:
ON THE DAY OF THE LAB:
1. Thoroughlychillthe70%isopropylalcohol(rubbingalcohol)beforethestudentsperformtheexperiment.
• Storeitinthefreezerforseveralhoursorovernighttoensurethatitisverycold.
• Usingacalibratedtransferpipet,transfer6mlof70%isopropylalcoholinto20testtubes.
• Placethealcohol-filledtubesbackinthefreezeroroniceuntilstudentsarereadytousethealcohol.
FREEZER
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INSTRUCTOR'S GUIDE Do Onions, Strawberries and Bananas Have DNA? EDVO-Kit #S-75
Please refer to the kit insert for the Answers to
Study Questions
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