DihybridCrossesAnswers
1. LetP=Purple,p=yellow
S=Smooth,s=wrinkled
PunnettSquare:
PS
Ps
pS
ps
2.
LetL=long,l=short P: LlhhxllHh
Parentalgeneration(P):PpSsxPpSs
Possiblegametes:PS,Ps,pS,psxPS,Ps,pS,ps
PS
Ps
pS
ps
PPSS PPSs PpSS PpSs
PPSs PPss PpSs Ppss
PpSS PpSs ppSS ppSs
PpSs Ppss ppSs ppss
PhenotypicRatio:
9Purple,smooth
3Purple,wrinkled
3Yellow,smooth
1Yellow,wrinkled
H=hairless,h=hairy
Gametes:Lh,lh,Lh,lhxlH,lh,lH,lh
Lh
lh
Lh
lh
lH LlHh llHh LlHh llHh
lh
Llhh llhh
Llhh llhh
lH LlHh llHh LlHh llHh
lh
Llhh llhh
Llhh llhh
Tohaveshortwings
andhairlessbody,it
hastobellH_,so25%
(4/16)oftheoffspring
shouldhaveshort
wingsandhairless
bodies.
3. LetC=crested,c=plain B=black,b=red
P:ccBBxCCbb
F1
cB
Gametes:cBxCb
Cb
CcBb
AllF1areheterozygousforCrestedandBlack.Whentheyarecrossed:
F1:CcBbxCcBb
Gametes:CB,Cb,cB,cbxCB,Cb,cB,cb
CB
CB
CB
CB PhenotypicRatio:
CB CCBB CCBb CcBB CcBb 9Crested,Black
CB CCBb CCbb CcBb Ccbb3Crested,red
3Black,Black
cB CcBB CcBb ccBB ccBb
1Black,red
cB CcBb Ccbb ccBb ccbb
4. LetB=black,b=red
S=solid,s=spotted
P:Male:S_B_xFemale:S_bb
Pups:2S_B_,2S_bb,1ssB_,1ssbb
Sincesomeofthepuppieshavebothrecessiveallelesforeachtrait,bothparentsmusthavehad
onetogivethem.Therefore,theparentsare:SsBb(male)andSsbb(female).
5. LetB=black,b=chestnut
T=trotter,t=pacer
P:BBTt(motherhadtogivehimtherecessivetallele)xBbTT
Tobeachestnuttrotter,itwouldhavetohavebbT_.Sincethefatherhasnobtogive,thereisa
0%chanceofgettingchestnuttrotters.
6. A)tGX,tGx
B)ABY,ABy,AbY,Aby,aBY,abY,aby,aBy(shouldbeeightpossibilities:there’stwopossible
allelesat3genes:23=8)
7. LetC=curly,c=straight B=brown,b=blue
P:B_ccxbbC_
Kids:bbC_,B_cc
Sincetherearekidswithbb,theymusthavereceivedoneballelefromeachparent.Sincethere
arekidswithcc,theymusthavereceivedonecallelefromeachparent.Thereforetheparents
areBbccandbbCc.