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HowDoAminoAcidSequences ProvideEvidence forEvolution?
Discussion:
Atechniqueusedtodetermineevolutionaryrelationshipsistostudythebiochemicalsimilarityof
organisms. Thoughmolds,aardvarks,andhumansappeartohavelittleincommonphysically,astudyoftheirproteinsrevealscertainsimilarities. Biologistshaveperfectedtechniquesfordeterminingthesequenceofaminoacidsinproteins.Bycomparingtheaminoacidsequencesinhomologousproteinsofsimilarorganismsandofdiverseorganisms,evolutionaryrelationshipsthatmightotherwisegoundetectedcanbedetermined. Biologistsbelievethatthegreaterthesimilaritybetweentheaminoacidsequencesoftwoorganisms,theclosertheirrelationship. Conversely,thegreaterthedifferences,themoredistanttherelationship. Inthisinvestigationyouwillcompareaminoacidsequencesinproteinsofseveralvertebrates. Youwillalsostudyaminoaciddifferencesandinferevolutionaryrelationshipsamongsomediverseorganisms.
Problem:
Procedure:PartA:
L ExamineFigure19-1whichcomparescorrespondingportionsofHEMOGLOBINmoleculesinhumansand5othervertebrateanimals.ThesequenceshownisonlyaPORTIONofachainmadeupof146aminoacids.ThenumbersinFigure19-1indicatethePOSITIONofaparticularaminoacidinthechain.
2. Inquestion IofPartAonthedatasheet,noticethattheabbreviatednamesoftheaminoacidsinhumanhemoglobinareprinted. Intheappropriatespacesinnumber1,writetheabbreviatednameofeachaminoacidinchimpanzeehemoglobinthatisDIFFERENTfromthatinhumanhemoglobin. IftherearenodifferencesleavethespacesBLANK.
3. Fortheremainingorganisms,writetheabbreviatednamesofanyaminoacidsthatDONOTcorrespondtothoseinhumanhemoglobin. NOTE: Alwaysbesurethatyoucomparetheaminoacidsequenceforeachorganismwiththatofthehuman,andnottheorganismonthelineabove.
4.CompleteTable19-1,onthedatasheet,afterSteps1-3aredone.
Figure19-1
87888990919293949590979899100101
Human THR LEUSERGLULEUHIS CYSASPLYSLEUHISVALASPPROGLUChimpanzee THR LEUSEAGLULEU HIS CYSASPLYSLEU HIS VALASPPROGLUGorilla THR LEUSERGLULEU HIS CYSASPLYSLEU HIS VALASPPROGLU
Rhesusmonkey GLN LEUSERGLULEUHISCYSASPLYSLEUHISVALASPPROGLUHorse ALA LEUSERGLULEUHIS CYSASPLYSLEU HIS VALASPPROGLUKangaroo LYS LEUSERGLULEU HIS CYS ASPLYSLEU HIS VALASPPROGLU
102103104105106107108109110111112113114115116
Human ASN PHEARGLEULEU GLYASNVALLEUVALc'is VALLEUALAHISChimpanzee ASN ·PHEARGLEULEU GLYASNVALLEUVALCYSVALLEUALA HISGorilla ASN PHELYS LEULEUGLYASN VALLEUVALCYSVALLEUALA HIS
Rhesusmonkey ASN PHELYSLEULEU GLYASNVALLEUVALCYSVALLEUALAHISHorse ASN PHEARGLEULEUGLYASNVALLEUALALEU VALVALALAARGKangarooASN PHELYSLEULEUGLYASN ILE ILE VAL ILE CYSLEUALAGLU
PartB:
Anothercommonlystudiedproteiniscytochromec.Thisprotein,consistingof104aminoacids,islocatedinthemitochondriaofthecells.Itisarespiratoryenzyme. ExamineFigure19-2. Usinghumancytochromecasastandard,theaminoaciddifferencesbetweenhumansandanumberofotherorganismsareshown.
1. Onyourdatasheet, makeaside-bargraph,toshowtheaminoaciddifferencesbetween humansandother organisms. Youwillhaveonebarforeachdifference.
2.Usethebargraphtoanswertheanalysisquestionsonthedatasheet.
Figure19-2
SpeciesPairings / NumberofDifferencesHuman·chimpanzee / 0
Human•fruitfly / 29
Human.horse / 12
Human.pigeon / 12
Human.rattlesnake / 14
Human•redbreadmold / 48
Human•rhesusmonkey / 1
Human.screwwormfly / 27
Human•snappingturtle / 15
Human·tunafish / 21
Human·wheat
Fig•.1!J.2 / 43
PartC:
1. ExamineFigure193. Inthisfigurethecytochromecofafruitflyisusedasastandardincomparingaminoaciddifferencesamongseveralorganisms.
2. Onyourdatasheet,construct aside-bargraphofthesedifferences.
3. Usethebargraphtoanswertheanalysisquestions onthedatasheet.
Figure19-3
SpeciesPairingsNumberof
Differences
Fruit fly-dogfishshark26
Fruit fly·pigeon25·Fruitfly·screwwormfly 2
Fruit fly·silkwormmoth15
Fruit fly·tabaccohornwormmoth14
Fruit fly·wheat47
Fig.19·3
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PartA:
Table1:Positions87-96
DataSheet:AminoAcid
Table2: Positions97-106
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Human
THRLEU SERGLULEU HISCYS ASPLYS LEU
979899100 101 102 103 104 105 106
Human
HISVALASPPROGLU ASNPHEARGLEULEU
ChimpanzeeChimpanzee
------
GorillaGorilla
------
RhesusmonkeyRhesusmonkey
------
HorseHorse
------
KangarooKangaroo
------
Table3:Positions107-116
107 IQ8 109 110 Ill 112 113 114 115 1!6
Human
GLYASNVALLEUVAL CYSVAL LEUALAHIS
Chimpanzee
------.Gorilla
Table19-1
------Rhesusmonkey
------
Horse
------
Kangaroo
------',------
AnalysisQuestions:PartA(Figure19-1}
1.InhowmanyPOSITIONSaretheaminoacidsthesameineachorganism?
2.Onthebasisoftheirhemoglobinsimilarity,which2organismsappeartobeMOSTcloselyrelatedtohumans?
3.Amongtheorganismcompared,which2appeartobeLEASTcloselyrelatedtohumans? _
Part8: UsetheinformationfromFigure19-2tocompletethefollowinggraph.
NomberofDifference.
SpeciesPainngs
0 2 4 6 8I 01214 161820222426283032343638404244464850
Human-humI
Human-chimpanz
Human-fru1.-.,
..·
Human-ho
Human-pigeo
Human-rattlesnak
Human-redbreadmol!!.
Human-Rhesusmonkey-
Human-screwwonnfly-
Human-snappingturtli
Human-tunatis•
Human-wheal
PartC:UsetheinformationfromFigure19-3tocompletethefollowinggraph.
NumberofDHferences
0 2 4 6 8 !(} 1214161820-?2-?426283032343638404244464850
Fruitfly-fruitHy
Fruitfly-dogfishshark
Fruitfly-:pigeon
Fruitfly-screwwonofly
Fruitfly-silkwormmoth
Fruitfly-tobaccohomwormmoth-
Fruitfly-wheat
AnalysisQuestions:
PartBandPartC(Figures19-2and193}
1.Onthebasisofdifferencesintheircytochrome c,what2organismsappeartobemostclosely?
relatedtohumans? ------
2.What2organismsappeartobeleastcloselyrelatedtohumans?------
3.Whichorganism(s)appear(s)tobemostcloselyrelatedtohumans;the snappingturtle,thetuna,therattlesnake,orthepigeon. Giveareasonforyouranswer.
4."Fruitfliesappeartobemorecloselyrelatedtosilkwormmothsthantheyaretoscrewwormflies." Doyouagreeordisagreewiththisstatementbasedontheinformationprovidedin19-3.Givereasonstosupportyouranswer.
5.Nametheorganismsthatappearstobeequallyrelatedtohumansonthebasisofcytochromesimilarity inFigure19-2.------
6."Fruitfliesandhumanshaveaboutthesameevolutionary relationship towheat." DoyouagreeordisagreewiththisstatementbasedontheinformationprovidedinFigure19-3.Defendyouranswer.