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Lesson The Making of the TheFittest: Making of the Fittest Natural Selection and Adaptation Natural Selection and Adaptation Educator MaterialsLESSON TEACHERMATERIALS INTRODUCTIONTOTHEMOLECULARGENETICSOFTHE COLORMUTATIONSINROCKPOCKETMICE OVERVIEW TheselessonsserveasanextensiontotheHowardHughesMedicalInstituteshortfilmTheMakingoftheFittest: NaturalSelectionandAdaptation.Studentswilltranscribeandtranslateportionsofthewild-typeandmutantrock pocketmouseMc1rgene.BycomparingDNAsequences,studentsidentifythelocationsandtypesofmutations responsibleforthecoat-colorchangedescribedinthefilm.Studentswillansweraseriesofquestionstoexplain howachangeinaminoacidsequenceaffectsthefunctionalityoftheMC1Rprotein,andhowthatchangemight directlyaffectthecoatcoloroftherockpocketmousepopulationsandthesurvivalofthatpopulation. KEYCONCEPTSANDLEARNINGOBJECTIVES • • Amutationisarandomchangetoanorganism’sDNAsequence. Mostmutationshavenoeffectontraits,butsomemutationsaffecttheexpressionofageneand/orthe geneproduct. • Theenvironmentcontributestodeterminingwhetheramutationisadvantageous,deleterious,orneutral. • Naturalselectionpreservesfavorabletraits. • Variation,selection,andtimefueltheprocessofevolution. • Boththetypeofthemutationanditslocationdeterminewhetherornotitwillhaveaneffecton phenotype(advancedversiononly). Studentswillbeableto: • transcribeandtranslateaDNAsequence. • connectDNAchangestophenotype. • analyzeandorganizedata. CURRICULUMCONNECTIONS Curriculum NGSS(April2013) CommonCore(2010) APBiology(2012–13) IBBiology(2009) Standards HS-LS1-1,HS-LS3-1,HS-LS3-2,HS-LS4-2,HS-LS4-4,HS-LS4-5 HS.LS1.A,HS.LS4.B,HS.LS4.C CCSS.ELA-Literacy.RST.9-10.3,CCSS.ELA-Literacy.RST.9-10.4, CCSS.ELA-Literacy.RST.9-10.7 1.A.1,1.A.2,3.A.1,3.C.1,4.B.1 3.5,4.1,4.3,5.4,7.3,7.4,D.2,G.1 KEYTERMS evolution,naturalselection,variation,trait,mutation,adaptation TIMEREQUIREMENT Theseactivitiesaredesignedforone50-minuteclassperiodincludingshowingthefilm.Additionaltimeforthe analysisquestionsmightberequiredforhomeworkdependingonstudents’pace.Bothactivitiescoverthesame material,butactivity2hasadditionalmaterialcoveringintracellular,transmembrane,andextracellulardomains. www.BioInteractive.org PublishedFebruary,2017 Page1of8 Lesson The Making of the Fittest: The Making of the Fittest Natural Selectionand andAdaptation Adaptation Natural Selection LESSON Educator Materials TEACHERMATERIALS SUGGESTEDAUDIENCE Activity1:Theactivityisdesignedforhighschoolbiology(primarilyfirst-yearbiology,bothregularandhonors). Activity2:TheactivityisdesignedforAPandIBhighschoolbiologyandintroductorycollegebiology. PRIORKNOWLEDGE Studentsshouldbefamiliarwiththedefinitionsof“gene”and“protein.”Theyshouldalsobecomfortablewith basicmoleculargenetics,includingafamiliaritywiththeprocessesoftranscriptionandtranslation.Finally, studentsshouldunderstandthataprotein’saminoacidsequencedeterminesitsstructure,whichdeterminesits function. MATERIALS Studentswillneed: geneticcodechart(providedinstudentmaterials) blue,red,andgreencoloredpencils TEACHINGTIPS • • Ifyoudonothaveaccesstoacolorprintertoprintthechartonpage2ofthisdocument,youshould comparestudents’worktohowthechartsbelowappearonyourcomputerscreen. Youcouldassignanalysisquestionsashomeworktoreducetheamountofclasstimerequiredforthis lesson. ANSWERKEYACTIVITY1 GENETABLE1:WILD-TYPEMC1RGENE(LIGHTCOAT-COLORPHENOTYPE) DNA mRNA Amino Acid 015 TTG AAC AGG UCC TGG ACC GCG CGC TGT ACA CCG GGC CAA GUU 022 GGA CCU Asn Ser Thr Arg Thr Gly Val Pro DNA mRNA Amino Acid 105 CGG GCC GAC CUG CGG GCC TGG ACC GCC CGG CAC GUG TGA ACU 112 CAC GUG Ala Leu Ala Thr Arg Val Thr Val DNA mRNA Amino Acid 154 TCA AGU TAA AUU CAC GUG TGT ACA GAC CUG GGG CCC GCC CGG 161 CGA GCU Ser Ile Val Thr Leu Pro Arg Ala DNA mRNA Amino Acid 209 GTG CAC TAC AUG GAA CUU 212 CGT GCA His Met Leu Ala www.BioInteractive.org PublishedFebruary,2017 Page2of8 Lesson The Making of the Fittest: The Making of the Fittest Natural Selectionand andAdaptation Adaptation Natural Selection LESSON Educator Materials TEACHERMATERIALS DNA mRNA Amino Acid 230 GAA CUU CAG GUC GTG CAC GTT CAA CCA GGU AAG UUC GCT CGA 237 GAG CUC Leu Val His Gln Gly Phe Arg Leu GENETABLE2:MUTANTMC1RGENE(DARKCOAT-COLORPHENOTYPE) DNA mRNA Amino Acid 015 TTG AAC AGG UCC TGG ACC ACG UGC TGT ACA CCG GGC CAA GUU 022 GGA CCU Asn Ser Thr Cys Thr Gly Val Pro DNA mRNA Amino Acid 105 CGG GCC GAC CUG CGG GCC TGG ACC ACC UGG CAC GUG TGA ACU 112 CAC GUG Ala Leu Ala Thr Trp Val Thr Val DNA mRNA Amino Acid 154 TCA AGU TAA AUU CAC GUG TGT ACA GAC CUG GGG CCC ACC UGG 161 CGA GCU Ser Ile Val Thr Leu Pro Trp Ala 209 GTG CAC TAC AUG GAG CUC 212 CGT GCA His Met Leu Ala DNA mRNA Amino Acid DNA mRNA Amino Acid www.BioInteractive.org 230 GAA CUU CAG GUC GTG CAC GTG CAC CCA GGU AAG UUC GCT CGA 237 GAG CUC Leu Val His His Gly Phe Arg Leu PublishedFebruary,2017 Page3of8 Lesson The Making of the Fittest: The Making of the Fittest Natural Selectionand andAdaptation Adaptation Natural Selection LESSON Educator Materials TEACHERMATERIALS QUESTIONSANSWERKEY 1.Ingeneexpression,whichenzymeisresponsiblefortranscribingtheDNAsequenceintomRNAbyadding complementaryRNAnucleotides?RNApolymerase 2.Inaeukaryoticcell,wheredoestranscriptionoccur?Inthenucleus 3.Describetheprocessoftranslation. TranslationistheprocessofturninginstructionsfrommRNAintochainsofaminoacids.Itoccursinthe cytoplasmwiththehelpofribosomesandtRNA. 4.Inaeukaryoticcell,whatmainorganelleisinvolvedintranslation?Ribosome 5.ExplaintherelationshipbetweenDNAsequence,aminoacidsequence,andproteinstructureandfunction. StudentsmaysimplyrelateDNAsequencetoaminoacidsequence,andaminoacidsequencetothethreedimensionalshapeoftheprotein.Anexampleofastudentresponsemaybe:“DNAsequenceprovidesthecode fortheaminoacidsequence.Theaminoacidsequencedeterminesthestructureoftheprotein,whichaffects thefunctionoftheprotein.” 6.TheMc1rgenecodesforthemelanocortin1receptor(MC1R)protein. 7.IftheMC1Rproteinis317aminoacidslong,whyarethere954basepairsinthecodingregionofthegene? EachoftheaminoacidshasacorrespondingmRNAcodonandDNAtripletconsistingofathree-basesequence.A proteinthathas317aminoacidsthereforehasaDNAbasesequenceconsistingof951basepairs(317×3=951 basepairs).Thethreeadditionalbasepairscorrespondtoastopcodonforwhichthereisnocomplementary aminoacid.Thestopcodonsignalstheterminationoftranslation. 8.OfthefivemutationsyouidentifiedintheMc1rgene,howmanyare: 5substitutions;0insertions;0deletions 9.OfthefivemutationsyouidentifiedintheMc1rgene,howmanyare: 1silent;4missense;0nonsense 10.Micewiththewild-type(nonmutant)Mc1rgenehavelight-coloredfur.Whichpigmentisresponsibleforthis coloration?Pheomelanin 11.Usingtheinformationintheintroductiononmutationsandyourknowledgeofproteins,developahypothesis toexplainhowthechangesintheMC1Rprotein’saminoacidsequencemightaffectitsfunction. Sampleanswer:ThefourmissensemutationsintheMc1rgenechangetheaminoacidsequenceoftheMC1R protein,whichchangesthestructureoftheprotein.Thechangeinproteinstructurewillaffecttheprotein function. 12.Explainhowsilentmutationsaffectthestructureandfunctionoftheprotein. Silentmutationsdonotchangetheaminoacid,andthereforewillnotchangethestructureoftheprotein. Becauseaprotein’sstructureisrelatedtoitsfunction,silentmutationsdonotaffectthefunctionofthe protein. 13.Usingtheinformationprovidedintheintroductionunder“MC1RGene,”explainhowthemutantMC1Rprotein directlyaffectsarockpocketmouse’scoatcolor. TheaminoacidchangesintheMC1Rproteinmaychangethestructureandfunctionoftheprotein.Thisleads toincreasedproductionofeumelanin,whichresultsinthedarkcolor. 14.Mutationsareasourceofgeneticvariation.Inthefilm,Dr.Carrollsaysthatmutationsoccurrandomly.What doesthatmean? Sampleanswer:Itmeansthatmutationsdonotoccurforapurposeorforanypredeterminedresult. 15.Itisacommonmisconceptionthat“allmutationsarebad.”Usetheexampleofrockpocketmicetoexplain whythisisnottrue.Inyouranswer,explainhowthedarkcoatcolormutationcanbeanadvantagetosomemice andadisadvantagetoothers. Sampleanswer:Mutationscanresultinnewtraits.Theselectiveadvantageprovidedbyatraitdependsonthe environment.Forexample,onalightsubstrate,individualswithdark-coloredcoatswouldbeatadisadvantage www.BioInteractive.org PublishedFebruary,2017 Page4of8 Lesson The Making of the Fittest: The Making of the Fittest Natural Selectionand andAdaptation Adaptation Natural Selection LESSON Educator Materials TEACHERMATERIALS becausetheywouldstandoutmorethanindividualswithlight-coloredcoats,makingthemeasierforpredators tospot.However,inthedarklavaflowhabitat,thosesamedark-coloredindividualswouldhaveaselective advantagebecausetheywouldbebettercamouflagedthanlight-coloredindividuals.So,thestatementthat“all mutationsarebad”isincorrect,becausetherearedifferentselectivepressuresonthetraitsproducedby mutationsdependingonthehabitat.Therearealsosilentmutationsthatdonotchangetheresultingprotein; theseareneutral,neithergoodnorbad. 16.Useyourunderstandingofevolutionandtheinformationinthefilmtoexplainhowthedark-coloredmutation cametobesocommoninsomepopulationsofrockpocketmice.Bespecific. Sampleanswer:Thedark-coloredmousehasaselectiveadvantageinahabitatsuchasthePinacatelavaflow, whichhasadark-coloredsubstrate.Sincerockpocketmicereproducequicklyandoften,thefrequencyofthis favoredtraitwouldspreadrapidlythroughthepopulation.Anylight-coloredmiceinthedark-coloredhabitat wouldbeataselectivedisadvantage,thusdecreasingtheirgenefrequencyinfuturegenerations.Inthisway, favorabletraitsaccumulateandincreaseinfrequency—justasDarwinexplained. ANSWERKEYACTIVITY2 GENETABLES 024 GAG CUC His Leu GTG CAC 024 GAG CUC His Leu WILD-TYPEMC1RGENE(LIGHT-COLOREDCOATPHENOTYPE) 105 DNA CGG GAC CGG TGG GCC CAC TGA CAC mRNA GCC CUG GCC ACC CGG GUG ACU GUG CAT GUA 114 GTC CAG Amino Acid Val Gln CAT GUA 114 GTC CAG Val Gln 015 TTG AAC Asn MUTANTMC1RGENE(DARK-COLOREDCOATPHENOTYPE) AGG TGG ACG TGT CCG CAA GGA UCC ACC UGC ACA GGC GUU CCU Ser Thr Cys Thr Gly Val Pro GTG CAC DNA mRNA Amino Acid WILD-TYPEMC1RGENE(LIGHT-COLOREDCOATPHENOTYPE) 015 DNA TTG AGG TGG GCG TGT CCG CAA GGA mRNA AAC UCC ACC CGC ACA GGC GUU CCU Amino Asn Ser Thr Arg Thr Gly Val Pro Acid EXTRACELLULARDOMAINI DNA mRNA Amino Acid 105 CGG GCC Ala www.BioInteractive.org Leu Ala Thr Arg Val Thr Val MUTANTMC1RGENE(DARK-COLOREDCOATPHENOTYPE) GAC CGG TGG ACC CAC TGA CAC CUG GCC ACC UGG GUG ACU GUG Leu Ala Thr Trp Val Thr Val PublishedFebruary,2017 Page5of8 Ala EXTRACELLULARDOMAINIII Lesson The Making of the Fittest: The Making of the Fittest Natural Selectionand andAdaptation Adaptation Natural Selection LESSON Educator Materials TEACHERMATERIALS DNA mRNA Amino Acid 163 ACC UGG Arg Trp MUTANTMC1RGENE(DARK-COLOREDCOATPHENOTYPE) 154 TCA TAA CAC TGT GAC GGG ACC CGA AGU AUU GUG ACA CUG CCC UGG GCU GCC CGG 163 ACC UGG Ser Arg Trp Val Thr Leu Pro Trp Ala GCC CGG Ile WILD-TYPEMC1RGENE(LIGHT-COLOREDCOATPHENOTYPE) 154 DNA TCA TAA CAC TGT GAC GGG GCC CGA mRNA AGU AUU GUG ACA CUG CCC CGG GCU Amino Ser Ile Val Thr Leu Pro Arg Ala Acid INTRACELLULARDOMAINI 230 GAA CUU Leu www.BioInteractive.org MUTANTMC1RGENE(DARK-COLOREDCOATPHENOTYPE) CAG GTG GTG CCA AAG GCT GAG GUC CAC CAC GGU UUC CGA CUC Val His His Gly Phe Arg Leu TTT AAA 239 CCG GGC Lys Gly TTT AAA 239 CCG GGC Lys Gly PublishedFebruary,2017 Page6of8 WILD-TYPEMC1RGENE(LIGHT-COLOREDCOATPHENOTYPE) 230 DNA GAA CAG GTG GTT CCA AAG GCT GAG mRNA CUU GUC CAC CAA GGU UUC CGA CUC Amino Leu Val His Gln Gly Phe Arg Leu Acid DNA mRNA Amino Acid MUTANTMC1RGENE(DARK-COLOREDCOAT PHENOTYPE) 208 212 DNA CAC GTG TAC GAG CGT mRNA GUG CAC AUG CUC GCA Amino Val His Met Leu Ala Acid INTRACELLULARDOMAINIII WILD-TYPEMC1RGENE(LIGHT-COLOREDCOATPHENOTYPE) 208 212 DNA CAC GTG TAC GAA CGT mRNA GUG CAC AUG CUU GCA Amino Val His Met Leu Ala Acid TRANSMEMBRANEV Lesson The Making of the Fittest: The Making of the Fittest Natural Selectionand andAdaptation Adaptation Natural Selection LESSON Educator Materials TEACHERMATERIALS QUESTIONSANSWERKEY 1.Usingtheaminoacidlocationnumbersprovidedabovethefirstandlastcolumnofeachtable,listthelocations ofthefiveaminoacidsthatcontainamutation. Theaminoacidlocationsare018,109,160,211,and233. 2.OfthefivemutationsyouidentifiedintheMc1rgene,howmanyarethefollowing: 5substitutions,0insertions,0deletions 3.OfthefivemutationsyouidentifiedintheMc1rgene,howmanyarethefollowing: 1silent,4missense,0nonsense 4. a.Whichfouraminoacidlocations(seeQuestion1above)containthemissensemutations? Theaminoacidsare018,109,160,and233. b.ExplainthelinkbetweenDNAsequenceandproteinstructureandfunction. StudentsmaysimplyrelateDNAsequencetoaminoacidsequence,andaminoacidsequencetothethreedimensionalshapeoftheprotein.More-advancedstudentsshouldbeabletolinkthemutationtoachangein theprotein’sprimarystructure,whichaffectsotherlevelsofstructure(secondaryandtertiary).Allstudent responsesshoulddemonstrateanunderstandingofthelinkbetweenDNAandthesequenceofaminoacids thatdeterminesthestructure,andthereforefunction,ofaprotein. 5.Usingtheinformationonmutationsintheintroductionandyourknowledgeofproteins,developahypothesisto explainhowthechangesintheMC1Rprotein’saminoacidsequencemightaffectitsfunction. StudentsmightsuggestthatsincethefourmissensemutationsintheMc1rgenechangetheaminoacid sequenceoftheMC1Rprotein,theproteinwillnotfunctionproperly,asaprotein’sfunctionisdeterminedby itsstructure. 6.Manyproteins,includingMC1R,containseveralstructuraldomainsthatcanfoldandfunctionindependently fromtherest.ThedomainnameswereprovidedforeachportionofDNAsequenceyoutranslatedearlier.Answer thefollowingquestions. a.WhereistheMC1Rproteinfound,andwhatisitsfunction?Bespecific. Itisareceptorproteinembeddedinthemembraneofmelanocytes.Itisspecializedforpigmentproduction. b.WhichproteindomainscontainthefourMc1rmissensemutations?(Refertothegenetablesyoucompleted earlier.) Themutationat018isinExtracellularDomainI,themutationat109isinExtracellularDomainIII,themutation at160isinIntracellularDomainI,andthemutationat233isinIntracellularDomainIII. c.Define“extracellular.” Extracellularmeans“somethingoutsideofacell.” d.Define“intracellular.” Intracellularmeans“somethinginsideofacell.” e.Whyisitsignificantthatthefourmissensemutationsarefoundintheextracellularandintracellulardomainsof theprotein?Explainyouranswer.(Hint:ThinkaboutMC1R’sfunction.) Specificanswerswillvary,butstudentsshouldhavetheideathataproteinthatspansacellmembranehasa portionthatprojectsoutofthecell(extracellular)andaportionthatprojectsintothecell(intracellular).This typeofreceptorproteinusuallyfunctionsineithercelltransportorcellsignaling.Changesinthestructureof extracellularandintracellularportionscanchangethefunctionoftheproteininthesignalingpathwayorthe transportmechanism.(Note:Seethelesson“TheBiochemistryandCellSignalingPathwayoftheMc1rGene” formoredetailonthisconcept.) www.BioInteractive.org PublishedFebruary,2017 Page7of8 Lesson The Making of the Fittest: The Making of the Fittest Natural Selectionand andAdaptation Adaptation Natural Selection LESSON Educator Materials TEACHERMATERIALS 7.UsingtheinformationontheMc1rgeneintheintroductionandyourknowledgeofproteins,developa hypothesistoexplainhowthechangeinMC1Rproteinfunctionmightdirectlyaffectarockpocketmouse’scoat color.Bespecificandconsiderboththelight-coloredanddark-coloredphenotypes. Specificanswerswillvary,butstudentsshouldsuggestthatthenormalMC1Rreceptorproteinwillproduce relativeamountsofeumelaninandpheomelaninthatwillresultinthelightcoatcolor.Inaddition,thedarkcoloredmousepopulationcontainsthemutantMc1rgene,whichresultsinadifferentreceptorprotein.This changeinstructuremightleadtoincreasedproductionofeumelanin,whichresultsinthedarkcolor. 8.Explainwhythemutationataminoacidlocation211isnotassignificantastheotherfourmutations. Itisasilentmutation,sotheaminoacidinthatpositiondoesnotchange,nordoesthestructureofthespecific domain.Thisisimportantbecauseaprotein’sstructurerelatestoitsfunction.Nochangeinthestructure suggeststhatthereisnochangeinthefunctionofthisparticulardomainoftheprotein. 9.Mutationsareasourceofgeneticvariation.Inthefilm,Dr.SeanCarrollsaysthatmutationsoccurrandomly. Whatdoesthismean? Sampleanswer:“Itmeansthatmutationsdonotoccurforapurposeorforanypredeterminedresult.” 10.Itisacommonmisconceptionthat“allmutationsarebad.”Usetheexampleofrockpocketmicetoexplain whythisstatementisnottrue.Inyouranswer,explainhowthedarkcoat-colormutationcanbeanadvantageto somemiceandadisadvantagetoothers. Sampleanswer:“Mutationscanresultinnewtraits.Theselectiveadvantageprovidedbyatraitdependsonthe environment.Forexample,onalightsubstrate,individualswithdark-coloredcoatswouldbeatadisadvantage becausetheywouldstandoutmorethanindividualswithlight-coloredcoats,makingthemeasierforpredators tospot.However,inthedarklavaflowhabitat,thosesamedark-coloredindividualswouldhaveaselective advantagebecausetheywouldbebettercamouflagedthanlight-coloredindividuals.Sothestatementthat“all mutationsarebad”isincorrect,becausetherearedifferentselectivepressuresonthetraitsproducedby mutationsdependingonthehabitat.Therearealsosilentmutationsthatdonotchangetheresultingprotein; theseareneutral,neithergoodnorbad.” 11.Useyourunderstandingofevolutionandtheinformationinthefilmtoexplainhowthedark-coloredmutation cametobesocommoninsomepopulationsofrockpocketmice.Bespecific. Sampleanswer:“Thedark-coloredmousehasaselectiveadvantageinahabitatsuchasthePinacatelavaflow, whichhasadark-coloredsubstrate.Sincerockpocketmicereproducequicklyandoften,thefrequencyofthis favoredtraitwouldspreadrapidlythroughthepopulation.Anylight-coloredmiceinthedark-coloredhabitat wouldbeataselectivedisadvantage,thusdecreasingtheirgenefrequencyinfuturegenerations.Inthisway, favorabletraitsaccumulateandincreaseinfrequency—justasCharlesDarwinexplained.” AUTHOR AnnBrokaw APBiologyTeacher RockyRiverHighSchool RockyRiver,Ohio www.BioInteractive.org PublishedFebruary,2017 Page8of8