In certain breeds of chickens, the allele \"B\" is responsible for black feather
ID: 67326 • Letter: I
Question
In certain breeds of chickens, the allele "B" is responsible for black feathers whereas the contrasting allele "b" produces feathers that are white (except for flecks of black). Birds heterozygous for this pair of alleles have blue feathers. Another pair of alleles influences the shape of the feathers. "F" produces straight feathers whereas the contrasting gene form "f" results in the frizzled condition (twisted, brittle feathers). A bird heterozygous for this pair of alleles is mildly frizzled. Give the phenotypic ratios to be expected from each of the following crosses: a) A black, frizzled hen x a white straight rooster b) A white, frizzled hen x a blue, straight rooster c) A blue, mildly frizzled hen x a white, frizzled rooster d) A blue, mildly frizzled hen x a blue, mildly frizzled rooster
Explanation / Answer
BB: black feathers
bb: white feathers
Bb: blue feathers
FF: straight feathers
ff: frizzled feathers
Ff: mildly frizzled feathers
A.
BBff x bbFF
Gametes: Bf, bF
BbFf (blue mildly frizzled hen) 100 %
B.
bbFF x BbFF
Gametes of bbFF: bF,
Gametes of BbFF: bF, BF
bF
bF
BF
BF
bF
bbFF
bbFF
BbFF
BbFF
bF
bbFF
bbFF
BbFF
BbFF
bF
bbFF
bbFF
BbFF
BbFF
bF
bbFF
bbFF
BbFF
BbFF
bbFF: white, straight hen (8 / 16)
BbFF: blue, straight hen (8 / 16)
C.
BbFf x bbff
Gametes of BbFf: BF, Bf, bF, bf and Gametes of bbff: bf
bf
bf
bf
bf
BF
BbFf
BbFf
BbFf
BbFf
Bf
Bbff
Bbff
Bbff
Bbff
bF
bbFf
bbFf
bbFf
bbFf
bf
bbff
bbff
bbff
bbff
BbFf: blue, mildly frizzled (4 / 16)
Bbff: blue, frizzled hen (4 / 16)
bbFf: white, mildly frizzled hen (4 / 16)
bbff: white, frizzled hen (4 / 16)
D.
BbFf x BbFf
Gametes of both genotypes: : BF, Bf, bF, bf
BF
Bf
bF
bf
BF
BBFF
BBFf
BbFF
BbFf
Bf
BBFf
BBff
BbFf
Bbff
bF
BbFF
BbFf
bbFF
bbFf
bf
BbFf
Bbff
bbFf
bbff
BBFF: black, straight hen (1 / 16)
BBFf: black, mildly frizzled hen (1 / 16)
BbFF: blue, straight hen (2 / 16)
BbFf: blue, mildly frizzled hen (4 / 16)
BBFf: black, mildly frizzled hen (1 / 16)
BBff: black, frizzled hen (1 / 16)
Bbff: blue, frizzled hen (2 / 16)
BbFF: white, straight hen (1 / 16)
bbFf: white, mildly frizzled hen (2 / 16)
bbff: white, frizzled hen (1 / 16)
bF
bF
BF
BF
bF
bbFF
bbFF
BbFF
BbFF
bF
bbFF
bbFF
BbFF
BbFF
bF
bbFF
bbFF
BbFF
BbFF
bF
bbFF
bbFF
BbFF
BbFF
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