In chickens, the presence of feathers on the legs is due to a dominant allele (F
ID: 141859 • Letter: I
Question
In chickens, the presence of feathers on the legs is due to a dominant allele (F), and the absence of leg feathers is due to a recessive allele (f). The comb on the top of the head can be either pea-shaped, a phenotype that is controlled by a dominant allele (P), or a single comb controlled by a recessive allele (p). The two genes assort independently. Assume that a pure-breeding rooster that has feathered legs and a single comb is crossed with a pure-breeding hen that has no leg feathers and a pea-shaped comb. The F1 are crossed to produce the F2. Among the resulting F2, however, only birds with a single comb and feathered legs are allowed to mate. These chickens mate at random to produce F3 progeny.
What is the expected genotype ratio for the resulting F3 progeny?
Express your answer as three numbers separated by colons.
FFpp : Ffpp : ffpp =
Explanation / Answer
Feathered leg = F(dominant), absence of feather= f (recessive)
Pea shaped comb=P( dominant), single comb=p( recessive)
Parental generation; feathered legs and a single comb X no leg feathers and a pea-shaped comb
FFpp X ffPP
F1: FfPp
FfPp X FfPp
FP
Fp
fP
fp
FP
FFPP
FFPp
FfPp
FfPp
Fp
FFPp
FFpp
FfPp
Ffpp
fP
FfPP
FfPp
ffPP
ffPp
fp
FfPp
Ffpp
ffPp
ffpp
F2: single comb and feathered legs: Ffpp are allowed to mate
Ffpp X Ffpp
Fp
fp
Fp
FFpp
feathered legs and single comb
Ffpp
feathered legs and single comb
fp
Ffpp
feathered legs and single comb
ffpp
no legs feather and single comb
F3
Expected genotype ratio for the resulting F3 progeny =FFpp: Ffpp: ffpp = 1:2:1
FP
Fp
fP
fp
FP
FFPP
FFPp
FfPp
FfPp
Fp
FFPp
FFpp
FfPp
Ffpp
fP
FfPP
FfPp
ffPP
ffPp
fp
FfPp
Ffpp
ffPp
ffpp
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