Download Double Muscle: Using Pedigrees

Double Muscle: Using Pedigrees
Name _________________________
Introduction to Pedigrees
Geneticistsusepedigreestounderstandthegeneticrelationshipbetweenorganismsinafamily.In
thisworksheet,wewillpracticecreatingapedigreerelatingtodoublemusclingandmaking
predictionsfromthepedigree.
Abeefrancher,Walter,recentlyhadacalfborntohisherdwithunusuallylargemuscles.Lance,
anotheroneofhiscattle,seemstohavethesamecondition.Outofcuriosityandconcern,Walter
searchedtheInternetforanexplanationofthecalf’scondition.
Soon,Walterdiscoveredageneticconditionthatcausesdoublemusclingincattlewhentwo
recessive(dd)genesarepresent.ToWalter’srelief,theconditionitselfisnotfatal.Walterlearns
thatthedoublemuscletraithasadvantagesanddisadvantages.Double-muscledcattlehavea
higherbirthweight,ribeyearea,feedefficiency,andimprovedretailproductyield.However,cows
deliveringdouble-muscledcalveshavedifficultywithlaborduetothelargersizeofthecalfandthe
double-muscledcowsshowdecreasedfemalefertilityandlowerstresstolerance.
Inlightofthisinformation,Walterdecidestostarttrackingdouble-musclinginhiscattleviaa
pedigree.Walterneedssomehelpwithupdatinghiscurrentpedigreeforthecattleonhisland.
Belowisthepedigreewithlimitedinformationrecorded.
Female Male
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Using Pedigrees
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Activity 2: Amending the Pedigree and Determining Genotypes
HelpWalteroutbyaddingthefollowinginformationtothepedigree:
1. JessyandKirkhadtwomorecalvesafterNero:Omar(amale)andPenelope(afemale).
2. Penelopeistheyoungfemalecalfwhoisdouble-muscled.
3. WaltertalkedwiththepreviousownersofDora.Accordingtothepreviousowners,Dora
oncehadamalecalfthatwasdouble-muscled.
4. WalteralsorevealsthatAlexhasneverbeenonhisfarm.WalterhadBellaartificially
inseminatedwithspermfromAlex.AmidstthepaperworktellingWalteraboutAlex’s
genetichistory,heseesthatdouble-musclingisNOTsomethingAlexisacarrierfor.
Teachernote:ThefactthatBellawasartificiallyinseminatedmaymeanWalter,thefarmer,
haslessphenotypicorgenotypicinformationaboutthebullthanotherbullshehasraised
himself.Waltertooktheinitiativetoaskaboutthebull’sgenotypeorthephenotypic
informationofhisoffspringtogetadditionalinformationaboutthebullwhichwillhelpWalter
makepredictionsabouthisherd.
UpdatedPedigree
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Using Pedigrees
(continued)
KnownandUnknownGenotypes
Teacherrefresher:
Genotypeisthealleliccompositionofacellororganism,usuallyrepresentedwithamixof
capitalandlowercaseletters(suchasDD,Dd,anddd).
Phenotypeisthephysicalappearanceofananimal.Inthisinstance,youcanseeiftheanimalhas
doublemusclesorisnormal.
Theshadedsymbolsinthepedigreeaboveprovideyouwithphenotypicinformationthatyou
canusetohelpdeterminegenotypicinformation.
Inpedigrees,themalesaresquaresandthefemalesarecircles.Ahorizontallinegoingfroma
maletoafemaleisamating.Horizontallineswithsmallverticallinesattachedtosquaresor
circlesindicateoffspringthataresiblings.
AnswerthefollowingquestionsaboutthegenotypesofthecattleinWalter’sherd.
1. WhatdoyouknowaboutPenelope’sgenotype?
dd
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Using Pedigrees
(continued)
2. WhatdoyouknowaboutKirk’sgenotype?
Dd
3. WhatdoyouknowaboutJessy’sgenotype?
Dd
4. WhatdoyouknowaboutFaith’sgenotype?
DDorDd
5. WhatdoyouknowaboutErik’sgenotype?
DDorDd
6. WhatdoyouknowaboutNero’sgenotype?
DDorDd
7. CouldGailbeacarrierofthedouble-musclegene?DrawaPunnettsquaretojustifyyour
answer.
Yes.CodyiseitherDdorDD.Whetherhe’sDDorDd,Gailcanstillbeacarrier.
8. CouldMissybeacarrierofthedouble-musclegene?DrawaPunnettsquaretojustifyyour
answer.
Yes.
StudentswillneedtoshowaPunnettsquareof
Missy’sparents,HenryandIzzy.
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Using Pedigrees
(continued)
9. WhichcattleinWalter’sherdcouldbecrossedtoguaranteeadouble-muscledoffspring?
PenelopeandLancearebothddforthedoublemusclemutation.Iftheywerecrossed,they
wouldhavea100%chanceofproducingonlydouble-muscledoffspring.
10. IfWalterwantstoavoiddouble-muscledoffspring,whichcattleshouldhecross?Why?
Alexistheonlyknownbullthatisnotacarrier.Therefore,crossingAlexwithanycowthat
isnotdouble-muscledwillproduceoffspringthatarenotdoublemuscled.
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