Biology: Cell Division and Cancer
Transcript of Biology: Cell Division and Cancer
HS9-12,Biology:CellDivision&Cancer©AmbitiousScienceTeaching2017
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CancerCells [PhotobyDr.CecilFoxviaWikimediaCommons]
Biology:CellDivisionandCancer
HighSchool9-12 CorinMaloneAuburnRiversideHighSchool,AuburnSchoolDistrictMaterialsadaptedfrom“NotAnOldPerson’sDisease”byNationalCenterforCaseStudyTeachinginScience*and“ACaseofSkinCancer”byScienceTake-Out**
* http://sciencecases.lib.buffalo.edu/cs/ ** http://www.sciencetakeout.com/
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Anchoringphenomenon:
Sofia,ayoungfair-skinnedwoman,observedconcerningchangestoamoleonherleg.Sofia’smoledemonstratedthecharacteristicsofmelanomaasdefinedbytheABCDEs1.Herconcernledhertoaskindoctorforfurtherdiagnosisthroughbiopsy.Thebiopsyrevealsthatshedoesinfacthavemelanoma,anaggressiveformofskincancer.
Essentialquestionaboutphenomenon/unit:
● Howdodifferentcellswithintheskinfunctiontoprovideprotectionagainsttheelementslikeultraviolet(UV)light?
● WhateffectdoesUVlighthaveoncellsandDNA?● Whataretheeffectsofmutationsonthefunctioningoftheproteins?
● Whyandhowdocellsdivide?
● Whatismelanomaandwhyisitsodangerous?
Scientificexplanation:Sofia’sskiniscomposedofthreelayers,theepidermis,dermisandhypodermis.Itisthefirstlayer,theepidermis,whichprovidesherbodyprotectionfromtheelements,includingUVlight.Theepidermisismadeoftwotypesofcells,keratinocytesandmelanocytes.Keratinocytesformmostoftheepidermisandtakethebruntoftheenvironmentalexposure;whilemelanocytesproducethepigmentmelaninthatisdistributedtokeratinocytes.Melaninnotonlygivesskinitspigmentation,butmoreimportantlyprotectstheDNAthatlieswithineachcell’snucleusagainstUVdamagebyabsorbingandscatteringtheenergy.ThemoremelaninapersonproducesthemoreUVprotectiontheyhave.Molesareclumpsorclustersofmelanocytesthatappearatthesurfaceoftheskinduringthecourseofagingandmoresunexposure.
Sofia’squestforatanthroughoutherlifeexposedhertomoreandmoreUVlight.WhenexposedtoUVlight,theenergycausedtwonucleotideswithinDNAtosticktogethercausingakinkinthedoublehelix.Mostofthetimethekinkcanbefixedwithcellmachinery,butifthekinkcannotbefixedthecellwilldieduetotheinabilitytoreplicateitsDNA.{WhencellsareexposedtotoomuchUV,morepartsoftheDNAaredamagedandthecelldies.}Onsomeoccasions,thecellmachineryinaccuratelyfixedtheDNAbyreplacingthejoinednucleotideswithdifferentnucleotides,causingamutationorachangeintheDNAsequence.
Whetheramutationisharmful,helpful,orneutraldependsonseveralfactors,butmostimportantlywhetherornotthemutationoccurredinasectionofDNAcalledagene.Genescontaintheinstructionsformakingproteinsthatcarryoutlifefunctions.Whenthesequenceofnucleotidesinthegeneisaltered,thestructureandfunctioningoftheproducedproteinisalteredaswell.
1asymmetrical,bordersuneven,colorsvaried,diameterlarger,evolving
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OneimportantlifefunctionwithinSofia’sskinisthecontinualregenerationofskincells.Inhealthycells,regenerationthroughcelldivisionoccursviaacontrolledprocesscalledthecellcycle,inwhichcellsgothroughphasesofgrowth,DNAreplicationandmitosiswithcheckpointsinbetweeneachphase.Ateachcheckpoint,proteinsproducedbycellcyclegenes(proto-oncogenesandtumorsuppressorgenes)assessifeachphasewassuccessfullycompleted.Innormalfunctioningcells,successfulcheckpointsleadtocontrolledcelldivisionanddifferentiation,whileunsuccessfulones’leadtoaprogrammedcelldeath,alsocalledapoptosis.
UnfortunatelyforSofia,oneormoregenesresponsibleforproducingtheproteinsneededforcheckpointsbecamemutated.Functioningcellcyclegenes(andcellcycleproteins)arenecessaryforthecontrolledcelldivision.Withoutthisability,hermelanocytesbegantodivideuncontrollablyleadingtothechangessheobservedinhermoleandthediagnosisofmelanoma.
TheobservedchangesofSofia’smolewerethesignsofalargerproblemoccurringbeneaththeskin.AfteryearsofUVlightexposure,atleastoneofSofia’smelanocyteswithinhermolehadmutatedcellcyclegenes.Thesemutatedcellcyclegenesdisruptedthefunctionoftheproteinsthattheycodeforandresultedintheuncontrolledcelldivisionofthatmelanocyte.Asthatmelanocytebegantodivideuncontrollably,itproducedtheobservedchangesinthemolebutalsoproducedatumorbeneaththeskin.Continuedgrowthofthetumorcouldleadtomoreseriousformsofmelanoma,inwhichindividualmelanocytesbreakofffromthetumorandspreadthroughthebloodstreamtootherpartsofthebody.Whenacancercellspreadsfromitsoriginaltumortootherpartsofthebodyitcandisruptthefunctioningofotherorgansandpotentiallyleadtodeath.Thebestapproachforreducingone’sriskfordevelopingmelanomaandothertypesofskincanceristoreduceUVlightexposure.
NGSSPerformanceExpectationsaddressedinthisunit:
Standard PE DCI CCC
HS-LS1-2 Developanduseamodeltoillustratethehierarchicalorganizationofinteractingsystemsthatprovidespecificfunctionswithinmulticellularorganisms.
LS1.A:StructureandFunctionMulticellularorganismshaveahierarchicalstructuralorganization,inwhichanyonesystemismadeupofnumerouspartsandisitselfacomponentofthenextlevel.
SystemsandSystemModels
HS-LS1-4 Useamodeltoillustratetheroleofcellulardivision(mitosis)anddifferentiationinproducingandmaintainingcomplexorganisms.
LS1.B.GrowthandDevelopmentofOrganismsInmulticellularorganismsindividualcellsgrowandthendivideviaaprocesscalledmitosis,therebyallowingtheorganismtogrow.Theorganismbegins
SystemsandSystemModels
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asasinglecell(fertilizedegg)thatdividessuccessivelytoproducemanycells,witheachparentcellpassingidenticalgeneticmaterial(twovariantsofeachchromosomepair)tobothdaughtercells.Cellulardivisionanddifferentiationproduceandmaintainacomplexorganism,composedofsystemsoftissuesandorgansthatworktogethertomeettheneedsofthewholeorganism.
MS-LS3-1 Developanduseamodeltodescribewhystructuralchangestogenes(mutations)locatedonchromosomesmayaffectproteinsandmayresultinharmful,beneficial,orneutraleffectstothestructureandfunctionoftheorganism.
LS3.A:InheritanceofTraitsGenesarelocatedinthechromosomesofcells,witheachchromosomepaircontainingtwovariantsofeachofmanydistinctgenes.Eachdistinctgenechieflycontrolstheproductionofspecificproteins,whichinturnaffectsthetraitsoftheindividual.Changes(mutations)togenescanresultinchangestoproteins,whichcanaffectthestructuresandfunctionsoftheorganismandtherebychangetraits.LS3.B:VariationofTraitsVariationsofinheritedtraitsbetweenparentandoffspringarisefromgeneticdifferencesthatresultfromthesubsetofchromosomes(andthereforegenes)inherited.
StructureandFunction
HS-PS4-4 Evaluatethevalidityandreliabilityofclaimsinpublishedmaterialsoftheeffectsthatdifferentfrequenciesofelectromagneticradiationhavewhenabsorbedbymatter.{Specifically,shorterwavelengthelectromagneticradiation(UV,X-rays,gammarays)canionizeatomsandcausedamagetolivingcells.}
PS4.B:ElectromagneticRadiationWhenlightorlongerwavelengthelectromagneticradiationisabsorbedinmatter,itisgenerallyconvertedintothermalenergy(heat).Shorterwavelengthelectromagneticradiation(ultraviolet,X-rays,gammarays)canionizeatomsandcausedamagetolivingcells.
CauseandEffect
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SummaryTableofActivitiesinUnit
Activity LearningTarget EvidenceStudentsCouldGain
ConnectiontoPhenomena
Activity1:Sofia,Melanoma&theABCDE’s(InitialModel)
Developamodeltoexplainyourthinkingaboutthegrowthanddevelopmentofawoman’smoleovertime.
Sofia’smoleshowsallsignsofmelanoma(allABCDEs).
Developinitialmodelsusingpriorknowledgeandbackgroundstory.
Activity2:
HowWeGetOurSkinColor
(Interactiveanimationusingmodelstoexplainthestructureandfunctionoftheskin).
Useamodeloftheskintodescribethestructureandfunctionoftheepidermis.
Thetoplayerofourskinismadeoftwocellsthatworktogethertoprovideprotection.One(keratinocytes)formawaterproofbarrier,theother(melanocytes)makemelanin.
MelaninhelpsprotectourskinfromUVlight.ItlookslikeanumbrellaoverthenucleusandabsorbsUVlight.ThishelpsprotectourDNAfromdamaging.
Amoleisaclusterofthecellsthatmakethepigmentmelanin,andarenotgenerallycancerous.
HS-LS1-2● Thetoplayerofourskin(epidermis)protectsusfromourenvironmentandismadeoftwocelltypes,melanocytesandkeratinocytes.
● Melanocytesmakemelaninandspreadthemelanintothesecondtypeofcell.
● Keratinocytesmakeupmostofthetoplayerofourskin.Thesecellseventuallydietoformawaterproofbarrier.
● MelaninmakesaprotectivecaplikeanumbrellaoverthenucleustoprotecttheDNAfromUVlight.
● Amoleisaclusterofmelanocytes.
Activity3:
SimulatingtheeffectsofUVlightonDNA
ModeltheeffectsofUVlightonDNA.
UVlightcancausechangesinourDNA.IftheDNAcannotbefixedamutationcouldresult.
HS-PS4-4● When exposed to UV light,
the energy caused two nucleotides within DNA to stick together causing a kink in the double helix.
● Most of the time the kink can be fixed with cell machinery, but if the kink cannot be fixed the cell will die due to the inability to replicate its DNA.
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Activity4:
TheEukaryoticCellCycle&CellDivision
Useamodelofthecellcycletoexplainthegrowthanddevelopmentofcellsovertime.
Thecellcycleisasequenceofeventsthatendswithcelldivision.Celldivisionallowslivingthingstogrowandrepairdamage.Checkpointsmakesurecelldivisionisnormal.
HS-LS1-4● Organisms require cell
division for growth and regeneration of dead cells.
● Cell division is a controlled process with phases.
● Between each phase are checkpoints that determine if the cell continues through to the next to ultimately divide.
● In normal cells, successful checkpoints lead to controlled cell division; while unsuccessful ones’ lead to apoptosis (cell death).
Activity5:
Genes,Mutations,andCancer
Criticallyreadscientificinformationtoexplainthecauseandeffectrelationshipbetweenmutationsandcancer.
Mutationshappeneverydayinourbodies.OurcellscanfixmostDNAdamage,sometimesitcan’t.Ifamutationhappensinspecialcellcyclegenes,itcouldleadcancer.Onecancercelldividesuncontrollablyandcantakeoverhealthycellsandmaybespreadtotherestofthebody.
MS-LS3-1● Whether a mutation is
harmful, helpful, or neutral depends on the mutation occurring in a section of DNA called a gene.
● Genes contain the instructions for making proteins. When the sequence of nucleotides in the gene is altered, the structure and functioning of the protein is also altered.
● When one or more genes responsible for producing the proteins needed for checkpoints in the cell cycle become mutated, uncontrolled cell division could result, leading to cancer.
Activity6:
SunSafetyLab
(Groupdesignedlabtocomparesunscreenandsunscreen
DesignandconductaninvestigationtocomparetheeffectivenessofsunscreentoreducingexposuretoUVlight.
DamagingUVlightcanbereducedthroughseveralmethods.
HS-PS4-4● The best approach for
reducing one’s risk for developing melanoma and other types of skin cancer is to reduce UV light exposure.
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alternatives.)
Activity7:
FinalModel/Explanation
Developamodelbasedexplanationtoexplainthegrowthanddevelopmentofawoman’smoleovertime.
TheobservedchangesofSofia’smolewerethesignsofalargerproblemoccurringbeneaththeskin.AfteryearsofUVlightexposure,atleastoneofSofia’smelanocyteswithinhermolehadmutatedcellcyclegenes.Thesemutatedcellcyclegenesdisruptedthefunctionoftheproteinsthattheycodeforandresultedintheuncontrolledcelldivisionofthatmelanocyte.Asthatmelanocytebegantodivideuncontrollably,itproducedtheobservedchangesinthemolebutalsoproducedatumorbeneaththeskin.Continuedgrowthofthetumorcouldleadtomoreseriousformsofmelanoma,inwhichindividualmelanocytesbreakofffromthetumorandspreadthroughthebloodstreamtootherpartsofthebody.Whenacancercellspreadsfromitsoriginaltumortootherpartsofthebodyitcandisruptthefunctioningofotherorgansandpotentiallyleadtodeath.
ModelTemplate
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AdditionalDocuments
InitialModelExample
ModelRevisionExample