Download Double Muscle: Genotype and Probability

Double Muscle: Genotype and Probability
Name _________________________
Introduction to the Double Muscle Trait
Insomeorganisms,includingcattle,arecessivegeneticmutationwillresultintheinactivationofa
genethatproducesmyostatin,anegativeregulatorofskeletalmusclegrowth.Cattlebornwithtwo
recessivealleleswillhavehighermusclemassandlessfat.Thedifferencesyouseebelowaredueto
hyperplasiaandhypertrophy.
Hyperplasia:theenlargementofanorganortissuecausedbyanincreaseinthe
reproductionofitscells
Hypertrophy:anenlargementofanorganortissuecausedbyanincreaseinthesizeof
individualcellswithintheorganortissue
Homozygousnormalmuscle,
DD
Heterozygousnormalmuscle,
Dd
Homozygousdoublemuscle,
dd
Thegeneticdifferencespicturedabovearepossiblebecauseofthelawofsegregation.Thecattleare
diploidorganisms,meaningtheyhavetwosetsofchromosomes.Duringsexualreproduction,the
twosetsofchromosomesaresegregated.Twohaploidcellscalledgametesarecreatedduring
meiosiswithonegenefromeachgenepairbeingcontributedtoeachgametes.Inthecaseofthe
myostatingene,theoffspringhaveaoneintwo(or50%)chanceofgettingeitherthenormal
muscleallele,D,orthemutatedallele,d.
APunnettsquareshowswhatgametesaremadebytheparentsandhowsegregatedallelescome
togethertoformoffspring.Punnettsquaresareusedtopredictthepossiblegenotypesofthe
offspringfromthetwoadultorganisms.
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Genotype and Probability
(continued)
Activity 1: Calculating the probability of genotypes
Inthisactivity,wewilllearnhowtomakemathematicalpredictionsbasedonthesegregating
allelesofcattleheterozygousfortheDoubleMuscle(Dd)gene.SeethePunnettsquarebelowto
visualizetheresultingoffspringfromtwoheterozygousindividualsbeingbredtogether.
Wecanthinkofthetwosidesofacoinasdominant(D)andrecessive(d)allelesfortheDouble
Musclegenepair.Thecoinalwayshastwosidessoitrepresentshowheterozygouscattlehaveboth
theDanddallelesinalloftheirsomaticcells.Theresultofacointoss,beingeitherheads(D)or
tails(d),representsthesegregationofallelesduringgameteproduction.Whenamaleorfemale
producesgametes,onlyonealleleofthetwoallelestheadultshaveispassedontotheoffspring.
Step1:Calculategametesforthebull.
Step2:Calculategametesforthecow.
Step3:Comparethebullandcowresults.
Step4:Predictoffspringgenotypesfromamatingofaheterozygousbullandcow.
Step5:Calculatetheprobabilityofeachoffspringtype.
Step6:Reflectingonthecointossingresults.
Step1:Fortheheterozygous(Dd)malebull,calculatethepercentageofDgametesanddgametes
created.
1. Youwillconductaprobabilityexperimentbyflippingacoin10times.Beforeflippingthe
coin,PREDICTtheoutcomeyouexpect.
!"
×100 =Heads(D)________% ×100 =Tails(d)__________%
!"
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Genotype and Probability
(continued)
2. Flipthecoin10timesandrecordyourdatainthespacebelow.
YourData
Tails
Heads
3. Addyourdatatotheboardatthefrontoftheclassroom.Thenfillinthetablebelowwith
theclassroomdata.
WholeClassData
Tails
Heads
4. Calculatethepercentheadsyourclassflipped.
#𝑜𝑓ℎ𝑒𝑎𝑑𝑠𝑓𝑙𝑖𝑝𝑝𝑒𝑑
𝑥100
#𝑜𝑓ℎ𝑒𝑎𝑑𝑠𝑎𝑛𝑑𝑡𝑎𝑖𝑙𝑠𝑓𝑙𝑖𝑝𝑝𝑒𝑑
5. Calculatethepercenttailsyourclassflipped.
#𝑜𝑓𝑡𝑎𝑖𝑙𝑠𝑓𝑙𝑖𝑝𝑝𝑒𝑑
𝑥100
#𝑜𝑓ℎ𝑒𝑎𝑑𝑠𝑎𝑛𝑑𝑡𝑎𝑖𝑙𝑠𝑓𝑙𝑖𝑝𝑝𝑒𝑑
6. Basedontheexperimentaldata(thedatafromtheboard),abouthowoftendoesabullwith
genotypeDdcreategameteswiththeDallele?
½or50%ofthetime
7. AbouthowoftendoestheDdbullcreategameteswiththedallele?
½or50%ofthetime
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Genotype and Probability
(continued)
Step2:Fortheheterozygous(Dd)femalecow,calculatethepercentageofDgametesandd
gametescreated.
Criticalthinking:YouareabouttocompletethesameproceduresforthefemaleDdcow,as
youdidwiththeDdbull.WillyourresultsbethesameorsimilarforthefemaleDdcow?
Whyorwhynot?
Theanswersforstep2will,infact,besimilarforthecowasitwaswiththebull.Thereason
forthisisthatboththecowandthebullarethesamegenotypeDd,sotheywillcreate
gametesthatareDanddatroughlythesamefrequencies.Sincetheanswersforthispartof
theworksheetshouldbethesameaspart1,lookatstep1fortheanswers.
1. Beforeflippingthecoin,whatpercentofcointossesdoyouexpecttobeheads(the
dominanttrait,D)ortails(therecessivetrait,d)?
!"
×100 =Heads(D)________% ×100 =Tails(d)__________%
!"
2. Flipthecoin10timesandrecordyourdatainthespacebelow.
YourData
Tails
Heads
3. Addyourdatatotheboardatthefrontoftheclassroom.Thenfillinthetablebelowwith
theclassroomdata.
WholeClassData
Tails
Heads
4. Calculatethepercentheadsyourclassflipped:
#𝑜𝑓ℎ𝑒𝑎𝑑𝑠𝑓𝑙𝑖𝑝𝑝𝑒𝑑
𝑥100
#𝑜𝑓ℎ𝑒𝑎𝑑𝑠𝑎𝑛𝑑𝑡𝑎𝑖𝑙𝑠𝑓𝑙𝑖𝑝𝑝𝑒𝑑
4
Genotype and Probability
(continued)
5. Calculatethepercenttailsyourclassflipped:
#𝑜𝑓𝑡𝑎𝑖𝑙𝑠𝑓𝑙𝑖𝑝𝑝𝑒𝑑
𝑥100
#𝑜𝑓ℎ𝑒𝑎𝑑𝑠𝑎𝑛𝑑𝑡𝑎𝑖𝑙𝑠𝑓𝑙𝑖𝑝𝑝𝑒𝑑
6. Basedontheexperimentaldata(thedatafromtheboard),abouthowoftendoesabullwith
genotypeDdcreategameteswiththeDallele?
½or50%ofthetime
7. AbouthowoftendoestheDdbullcreategameteswiththedallele?
½or50%ofthetime
Step3:Comparetheresultsofstep1and2.
1. Lookatyouranswertoquestion6instep1andstep2.Didyouhavesimilaranswersto
bothofthosequestions?Whyorwhynot?Hint:Thinkaboutsegregationofallelesandthe
genotypeofthemaleandthefemale.
Theanswersforbothofthestepsshouldbesimilar.Theyaresimilarbecausethemaleand
femaleareboththesamegenotype(Dd).Whensegregationhappens,about½oftheir
gameteswillhavetheDalleleandtheotherhalfwillhavethedallele.
Step4:Predictoffspringtypesfromamatingbetweentheheterozygousbullandcow.
Forthisportionoftheactivity,youwillworkinpairstolearnhowthesegregationofallelesinthe
bullandthecowimpactthetypeofoffspringthetwoanimalsareexpectedtoproduce.
1. Whatarethefourpossibleallelecombinationthatcanresultfromcrossingaheterozygous
bullandcow?
_____DD_____________Dd_____________dD____________dd________
2. These4combinationsrepresentwhat?*Hint:readthebackgroundinformationatthe
beginningofthisworksheet.
These4combinationsrepresenttheoffspringgenotypes.
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Genotype and Probability
(continued)
Step5:Calculatetheprobabilityofeachoffspringtype.
1. Eachstudentshouldhavetheirowncointoflip.Designateonepersontoflipcoin1to
representthesegregationofallelesinthemalebullandtheotherpersontoflipcoin2to
representthesegregationofallelesinthefemalecow.Itmaybehelpfultohavetwo
differenttypesofcoinstokeeptrackoftheallelescomingfromthemaleandfromthe
female.
2. Now,youandyourpartnerwillflipacoinatthesametime.Youwillmakeatallyinthe
squarebelowthatrepresentstheoutcomeofeachroundofcointossinginthePunnett
squarebelow.Youmaydoasmanyroundsofcointossingasyouthinkyoushouldinorder
toobtainaresultthatyouareconfidentrepresentstheexpectedoutcome.
Coin1(malegametes)
Heads(D)
Tails(d)
Coin2
(female
gametes)
Heads(D)
Tails(d)
Bothcoinswereheads Head(D)fromfemale,
(DD).
tail(d)frommale.
Tail(d)fromfemale,
head(D)frommale.
Bothcoinsweretails
(dd).
3. Addyourdatatotheboardatthefrontoftheroom.Onceeveryonehascompletedtheircoin
tosses,combinetheclassdataandwriteitinthechartbelow.
WholeClassData
Malegametes
Heads(D)
Tails(d)
Heads(D)
Bothcoinswereheads
(DD).
Head(D)fromfemale,
tail(d)frommale.
Tails(d)
Tail(d)fromfemale,
head(D)frommale.
Bothcoinsweretails
(dd).
Femalegametes
4. Calculatethetotalnumberoftossesbyallgroups(addupthenumbersinthefoursquares
fortheclassroomdata),writeyourresulthere.________________
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Genotype and Probability
(continued)
5. CalculatethepercentofcointossesthatwereDD,dD,Dd,anddd.Divideeachofthe
numbersyoufilledintothechartforquestion3ofthisstepanddivideitbythenumberyou
calculatedinquestion4ofthisstep.
Malegametes
Heads(D)
Tails(d)
Heads(D)
#𝑜𝑓𝐷𝐷𝑡𝑜𝑠𝑠𝑒𝑠
𝑥100
𝑡𝑜𝑡𝑎𝑙#𝑜𝑓𝑡𝑜𝑠𝑠𝑒𝑠
#𝑜𝑓𝐷𝑑𝑡𝑜𝑠𝑠𝑒𝑠
𝑥100
𝑡𝑜𝑡𝑎𝑙#𝑜𝑓𝑡𝑜𝑠𝑠𝑒𝑠
Tails(d)
#𝑜𝑓𝑑𝐷𝑡𝑜𝑠𝑠𝑒𝑠
𝑥100
𝑡𝑜𝑡𝑎𝑙#𝑜𝑓𝑡𝑜𝑠𝑠𝑒𝑠
#𝑜𝑓𝑑𝑑𝑡𝑜𝑠𝑠𝑒𝑠
𝑥100
𝑡𝑜𝑡𝑎𝑙#𝑜𝑓𝑡𝑜𝑠𝑠𝑒𝑠
Femalegametes
6. Whichofthefractionsbelowisclosesttoyourclass’sresultsforDD?
0 ¼
½
¾
1
7. Whichofthefractionsbelowisclosesttoyourclass’sresultsfordD?
0 ¼
½
¾
1
8. Whichofthefractionsbelowisclosesttoyourclass’sresultsforDd?
0 ¼
½
¾
1
9. Whichofthefractionsbelowisclosesttoyourclass’sresultsfordd?
0 ¼
½
¾
1
Step6:Implicationofcointossingresults.
1. Ifthetwoheterozygous(Dd)cattlehaveoffspring,whatfractionofthetimedoesitappear
thattheoffspringwillbedouble-muscled(dd)?
¼
2. Ifthetwoheterozygous(Dd)cattlehaveoffspring,whatfractionofthetimedoesitappear
thattheoffspringwillbenormal-muscled(DDorDd)?Hint:You’llneedtodosomeadding!
¼+¼+¼=¾
3. Usingyourknowledgeofbiologyandmathematics,explainhowyouareabletomake
predictionsaboutthegenotypeofoffspringbasedonthegenotypeoftwoparents.
Wecanmakepredictionsbecauseeachparenthastwoallelestheycouldpasson.Ifthey’re
twodifferentalleles,there’sa½chanceofpassingononeofthoseallelesortheotherone.
Wecanmultiplytheprobabilityofgettingaspecificallelefromoneparentbythe
probabilityofgettingaspecificallelefromanotherparenttodeterminehowoftenan
offspringwillgetaparticulargenotype.Wecanaddwhenwewanttoknowtheprobability
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Genotype and Probability
(continued)
ofgettingagenotypeinoffspringwhentherearemultiplewaysaparticulargenotype(such
asgettingDdanddD).
4. Didthenumberoftimesyoutossedthecoinhaveanimpactonthemathematicaloutcome
ofyourcointossexperiment?*Hint:Thinkabouthowoftenyouexpecttoflipaheadsora
tails.Ifyouflipthecointwice,willyougetwhatyouexpect?Asyouflipthecoinmoreand
moretimes,doyouthinkyouwillgetclosertothenumberofheadsandtailsyoushouldget
intermsofpercentage?
Asthestudentsflipthecoinsmoreandmoretimes,theyshouldnoticethattheygetcloser
andcloserto50%ofthecointossesbeingheadsand50%beingtails.Havingmoredata
meansthere’slesschance(orrandomerror)happeninginthedata.
5. Imaginethatwecouldtestforthesametraitinmice.Thegestationperiodformiceis19-21
dayscomparedto274daysforcattle.Inaddition,amouseproduces6-8offspringperlitter
comparedto1offspringproducedpercow.
Basedonyouranswerfrom#4ofthisstep,wouldyouratherworkwithatraitinmiceora
traitincattleforinheritancestudies?*Hint:Isthereanadvantagetoquicklyproducinglots
ofmiceascomparedtoafewcattle?
Theadvantageofmiceisthattheycanbreedquickly,soyoucanquicklygetdataand
minimizeerrorduetochance.
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