Download soap opera punnet square

SoapOperaGenetics
–GeneticstoResolveFamilyArguments1
I.Howcouldourbabybeanalbino?
TiffanyandJoehavejusthadababyandareverysurprisedtolearnthattheirbabyisalbino
withverypaleskinandhaircolor.Tiffany‘ssistercomesintovisitTiffanyandthenewbaby,
andJoegoesouttotalkwithhissisterVicky.
DidTiffanyhaveanaffair?
Joeisveryangry.HetellsVicky,"IthinkTiffanyhadanaffairwithFrank!He’stheonlyalbino
weknow.Obviously,TiffanyandIaren'talbino,soFrankmustbethefather."
Luckily,Vickyisabiologyteacher,sosheexplainshowtwoparentswithnormalskincolorcould
haveanalbinobaby.ShedrawsaPunnettSquaretoillustrateherexplanation.
1.DrawaPunnettSquaretoshowhowtwoparentswithnormalskincolorcouldhavean
albinobaby.UseafortherecessiveallelethatcanresultinverypaleskinandhaircolorandA
forthedominantallelethatresultsinnormalskinandhaircolor.
Joeisstillangryandhedoesn'tunderstandthePunnettSquare,sohedemandsabetter
explanation.Luckily,Vickyisapatientperson,sosheexplainsagainhowJoeandTiffanycould
haveanalbinobaby,makingsurethatJoeunderstandseachstepintheprocess.
2.Drawanew,morecompletePunnettSquaretohelpexplainhowinheritanceworks.Include
thegenotypesofbothparents,straightarrows(—>)torepresentmeiosis,wavyarrows(~~~>)
torepresentfertilization,andlabelsforeggs,sperm,andzygotes.
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ByIngridWaldron,DepartmentofBiology,UniversityofPennsylvania,2013.TeachersareencouragedtocopythisStudentHandoutfor
classroomuse.AWordfile(whichcanbeusedtoprepareamodifiedversionifdesired),TeacherNotes,comments,andadditionalactivitiesare
availableathttp://serendip.brynmawr.edu/exchange/bioactivities.
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Whyaren'tmorebabiesalbino?
Bynow,Joehascalmeddownandheisgettinginterested.HeasksVicky"Ifthat’showit
works,itseemsasthoughaquarterofallbabiesshouldbealbino.Howcometherearehardly
anyalbinobabies?"
3.WhatexplanationshouldVickygivetoanswerthisquestion?
Joeisstartingtofeelguiltyforgettingsomad.Hesays"Geez,Ifeellikeajerknow.Ishould
haveknownthatTiffanywouldnevercheatonme."Vickyresponds,"That'sokay.Youwere
upset.Let'sjustforgetaboutit."
WillTiffanyandJoe'snextbabybealbino?
Twoyearslater,Tiffanyispregnantagain,andsheandJoearediscussingwhethertheirsecond
babywillbealbino.Tiffanythinksthebabyprobablywillbealbino,butJoeremembersVicky's
explanation,andhetellsTiffany,"No,oursecondbabycan'tbealbinobecauseonlyoneoutof
everyfourofourchildrenshouldbealbino.Wealreadyhaveonealbinochild,soournextthree
childrenshouldnotbealbino."
4.IsJoeright?Explainwhyorwhynot.
5.WhatistheprobabilitythatTiffanyandJoe'ssecondbabywillbealbino?
Howdoyouknow?
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II.Werethebabiesswitched?
Twocoupleshadbabiesonthesamedayinthesamehospital.DeniseandEarnesthadagirl,
Tonja.DanielleandMichaelhadtwins,aboy,Michael,Jr.,andagirl,Michelle.Daniellewas
convincedthattherehadbeenamix-upandshehadthewronggirl,sinceMichaelJr.andTonja
werebothlight-skinned,whileMichellewasdarkskinned.Danielleinsistedonbloodtypetests
forbothfamiliestocheckwhethertherehadbeenamix-up.Inordertointerprettheresultsof
thebloodtypetests,youwillneedtounderstandthegeneticsofbloodtypes.
BloodTypes
TheABObloodtypesystemisthemajorbloodtypeclassificationsystemthatdetermineswhich
typeofbloodcansafelybeusedforatransfusion.ThefourbloodtypesintheABOsystemare
TypeA,TypeB,TypeAB,andTypeO.Thesebloodtypesrefertodifferentversionsof
carbohydratemolecules(complexsugars)whicharepresentonthesurfaceofredbloodcells.
Peoplewith: Have:
TypeAblood
TypeBblood
TypeAcarbohydratemolecules
ontheirredbloodcells
TypeBcarbohydratemolecules
ontheirredbloodcells
TypeABblood
TypeAandBcarbohydrate
molecules
ontheirredbloodcells
TypeOblood
NeitherAnorBcarbohydrate
molecules
ontheirredbloodcells
GeneticsofBloodTypes
Thesebloodtypesresultfromtheallelesofagenethatcancodefortwodifferentversionsofa
proteinenzymeoraninactiveprotein,asshowninthefollowingtable:
Allele Codesforaproteinthatis
IA
aversionoftheenzymethatputsTypeAcarbohydratemoleculesonthesurfaceof
redbloodcells
B
I
aversionoftheenzymethatputsTypeBcarbohydratemoleculesonthesurfaceof
redbloodcells
i
inactive;doesn'tputeithertypeofcarbohydratemoleculeonredbloodcells
1.Eachpersonhastwocopiesofthisgene,oneinheritedfromhis/hermotherandtheother
inheritedfromhis/herfather.Completethefollowingtabletorelategenotypestobloodtypes.
Genotype Thisperson'scellsmake:
BloodType
theversionoftheenzymethatputsTypeAcarbohydrate
IAIA
moleculesonthesurfaceofredbloodcells.
ii
theinactiveprotein.
IAi
boththeversionoftheenzymethatputsTypeAcarbohydrate
moleculesonthesurfaceofredbloodcellsandtheinactive
protein.
A
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2.InapersonwiththeIAigenotype,whichalleleisdominant,IAori?Explainyourreasoning.
3.Forthegenotypeslistedbelow,whichtype(s)ofenzymewouldthisperson'scellsmake?
Whatbloodtypewouldthepersonhave?
Genotype Willthisperson'scellsmaketheversionoftheenzymeneededto
attachthiscarbohydrateonthesurfaceofhisorherredbloodcells?
Blood
Type
IBIB
TypeA__yes__no;TypeB__yes__no
IBi
TypeA__yes__no;TypeB__yes__no
IAIB
TypeA__yes__no;TypeB__yes__no
Codominancereferstoinheritanceinwhichtwoallelesofageneeachhaveadifferent
observableeffectonthephenotypeofaheterozygousindividual.Thus,incodominance,
neitheralleleisrecessive—bothallelesaredominant.
4.Whichofthegenotypesresultsinabloodtypethatprovidesclearevidenceofcodominance?
Explainyourreasoning.
Werethebabiesswitched?
NowyouarereadytoevaluatewhetherEarnestandDenise'sbabygirlwasswitchedwith
MichaelandDanielle'sbabygirl.Thefollowingfamilytreesshowthebloodtypesforeach
personinbothfamilies.
5.WhatalleleforthebloodtypegenewillbepresentineacheggproducedbyDanielle?
Michaelcanproducespermwitheitherthe_____alleleorthe_____allele.
DrawthePunnettSquarethatshowsthepossiblegenotypesforDanielleandMichael's
children.Writeinthebloodtypeforeachgenotypetoshowthepossiblebloodtypesfor
DanielleandMichael'schildren.
IsitpossibleforDanielleandMichaeltohaveachildwhohastypeOblood?
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6.TocheckwhetherEarnestandDenisecouldhaveababywithTypeOblood,drawaPunnett
squareforafatherwhohasbloodTypeAandIAigenotypeandamotherwhohasbloodTypeB
andIBigenotype.Writeinthebloodtypeforeachchild'sgenotype.
7.WereEarnestandDenisetheparentsofTonjaorhadthehospitalmadeamistake?Explain
yourreasoning.
Whydothetwinslooksodifferent?
Now,Daniellewantstoknowhowhertwinscouldlooksodifferent,withMichellehavingdark
skinandMichaelJr.havinglightskin.First,Danielleneedstounderstandthattherearetwo
typesoftwins.Identicaltwinscomefromthesamezygotewhenadevelopingembryosplitsin
two,soidenticaltwinshaveexactlythesamegenes.
8.HowdoyouknowthatMichelleandMichaelJr.arenotidenticaltwins?
MichelleandMichaelJr.arefraternaltwins,theresultoftwoseparateeggs,eachfertilizedbya
differentsperm.MichelleandMichaelJr.inheriteddifferentallelesofthegenesforskincolor
becausetheeggandspermthatformedthezygotethatdevelopedintoMichellecarried
differentallelesofthegenesforskincolorthantheeggandspermthatformedthezygotethat
developedintoMichaelJr.
Tounderstandhowoneofthetwinscouldhavelightskinandtheotherdarkskin,wewill
considertwoallelesofoneofthegenesforskincolor.
Genotype Phenotype(skincolor)
BB
darkbrown
Bb
lightbrown
bb
tan
Noticethatforthisgeneaheterozygousindividualhasanintermediatephenotype,halfway
betweenthetwohomozygousindividuals.Thisiscalledincompletedominance.
9.Explainhowincompletedominancediffersfromadominant-recessivepairofalleles.(Hint:
Thinkaboutthephenotypesofheterozygousindividuals.)
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10.Explainhowincompletedominancediffersfromco-dominance.
11.Theparents,MichaelandDanielle,bothhavelightbrownskinandBbgenotype.Drawa
Punnettsquaretoshowhowtheseparentscouldhavetwobabieswithdifferentcolorskin–
onedarkbrownandtheothertan.
Obviously,peoplehavemanydifferentskincolors,notjustdarkbrown,lightbrown,ortan.The
reasonsforallthesedifferentskincolorsinclude:
• Multiplegenesinfluenceskincolor.
• Foratleastoneofthesegenes,therearemultipledifferentallelesthathavedifferent
effectsonskincolor.
• Skincolorisalsoinfluencedbytheamountofexposuretothesun.
12.Therelationshipsbetweengenotypeandphenotypearenotassimpleasshowninthechart
onthepreviouspage.Forexample,onepersonwithBbgenotypemayhavelightbrownskin,
butanotherpersonwithBbgenotypemayhavedarkbrownskin.Basedontheabove
information,explainhowthiscouldhappen.
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III.Idon'twanttohaveanydaughterswhoarecolorblindlikeme!
FrankandAwildaatBreakfast
Frank:Areyousureyouwanttowearthatnewshirttoworktoday?Agreenandredshirtlikethat
wouldbebetterforChristmas,notforSt.Patrick'sDay.
Awilda:Ohno!Notagain!Ihatebeingcolorblind!Ireallythoughtthisshirtwasjustdifferentshades
ofgreen.Where'sthered?
AtDinnerThatNight
Awilda:Weshouldtrytofindawaytomakesureweonlyhavesons,nodaughters.Idon'twanttohave
anydaughterswhomightbecolorblindandhavesomanyproblemslikeIdo.Colorblindness
wouldn'tmattersomuchforaboy.
Frank:Remember,thedoctorsaidthat,sinceI'mnotcolorblind,noneofourdaughterswouldbecolor
blind,onlyoursons.
Awilda:Idisagree.Ithinkourdaughterswillbecolorblindlikemeandoursonswillbenormallikeyou.
Frank:No,thedoctorsaidthatthegeneforcolorblindnessisontheXchromosome,soonlyoursons
willinherityourcolorblindness.
Awilda:Thatdoesn'tmakeanysense.GirlshavemoreXchromosomesthanboys,sogirlsshouldbe
morelikelytobecolorblind.
HelpFranktoexplaintoAwildawhytheirsonswillbecolorblindandtheirdaughterswillnotbecolor
blindbyansweringthefollowingquestions.
1.WhatarethegenotypesofAwildaandFrank?(SincethealleleforcolorblindnessislocatedontheX
chromosome,usethesymbolXcbforanXchromosomewiththerecessivealleleforcolorblindnessand
XCBforanXchromosomewiththedominantnormalallele.)
Awilda:
Frank:
2.DrawthePunnettsquareforthiscoupleandtheirchildren.InthisPunnettSquare,circleeach
daughterandusearrowstoindicateanycolorblindoffspring.
3.WriteanexplanationtohelpAwildaunderstandwhytheirsonswillbecolorblindeventhoughtheir
fatherhasnormalcolorvision.
4.Explainwhytheirdaughterswillnotbecolorblindliketheirmother.
5.ExplainwhyhavingtwoXchromosomesdecreasesaperson’sriskofcolorblindness,insteadof
increasingherrisk.
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IV.DogBreeder’sDilemma–DeafDalmatians
YourneighborbreedsDalmatiandogs,andsheasksforyourhelpsinceyourmotherhasbeen
braggingthatyougotaperfectscoreonyourgeneticstest.Yourneighborisconcerned
becausedeafnessisquitecommoninDalmatiandogs.Shehastwomaledogsthatshewantsto
useforbreedingwithsomeofherfemaledogs.Themaledogscanhear,butshedoesnotwant
touseanydogforbreedingifhecouldpossiblyfatherdeafpuppies.
1.Youassumethatdeafnessisduetoarecessivealleleforasinglegene.Whatarethe
possiblegenotypesforthemaledogsthatcanhear?(Usedfortherecessiveallelefordeafness
andDfortheallelefornormalhearing.)
2.Totestwhethereachofthemaledogsisheterozygousorhomozygous,yourecommendthat
yourneighbormateeachmaledogwithaspecifictypeoffemaledog.Whattypeoffemaledog
shouldyourneighboruseforthistest?Whatwouldthisfemaledog’sphenotypeandgenotype
be?
3.DrawtheappropriatePunnettSquarestoillustratehowthistestwoulddeterminewhether
eachofyourneighbor’smaledogsisheterozygousorhomozygous.InthePunnettsquares,
circleanyoffspringthatwouldbedeaf.
4.Yourneighborfollowsyouradviceandreportstheresultsshowninthefirstcolumnofthe
table.Completethemiddleandlastcolumnsofthetabletoshowtheadviceyouwouldgiveto
yourneighbor.
Outcomeof
Shouldtheownerusethisdogforbreeding
Howconfidentareyouof
mating
purposes?Whyorwhynot?
thisconclusion?
Firstfather:
5puppies,
1deaf
Secondfather: 6puppies,
0deaf
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Youareproudofyourworkasageneticsadvisorandyoushowthistabletoyourteacher,
hopingthatshemaygiveyousomeextracreditinyourbiologycourse.Sheresponds,"Ohno!I
hopeyoudidn'tgiveyourneighboraguaranteeonyouradvice."
Youareupsetandaskherwhatiswrong.Sheexplainsthatbiologistshavediscoveredthatthe
inheritanceofdeafnessisverycomplexandinvolvesmorethanonegene.Inhumansthereare
atleast40differentgenesthatcanresultindeafnessbycausingdefectsinthedevelopmentor
functionofdifferentpartsoftheearornervoussystem.Biologistsstillhavenotfiguredoutthe
genesresponsiblefordeafnessinDalmatians,buttheyknowthatmorethanonegeneis
involved.Becausethegeneticsiscomplexandnotwellunderstood,carefulbreedingcan
reducethechanceofdeafnessbutnoteliminatethepossibilityofdeafpuppies.
Youarestillfeelingupset,andyouaskyourteacher,"Doyoumeanthatallthestuffyoutaught
usaboutMendelandgeneticsisn'treallytrue?"
5.Howshouldsherespond?
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