do onions, strawberries and bananas have dna?

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

1.800.EDVOTEK • Fax 202.370.1501 • [email protected] • www.edvotek.com

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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


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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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



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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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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



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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.


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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

- - - - -



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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.


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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.



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Study Questions

1. DescribetheappearanceoftheisolatedDNA.

2. Whatisanucleus?

3. Whatarenucleotides?

4. Whatarechromosomes?

5. Whatdoescelllysismean?

6. WhydidthealcohollayerontopoftheDNAsolution?

7. WhywasitimportantnottomixthealcoholandDNAsolutions?

8. WhatpropertiesofDNAallowspooling?

9. Whatdifficultiesdidyouhaveinspooling?Why?

10. Howmanychromosomesdohumanshave?


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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

do onions, strawberries and bananas have dna?

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