2.In griffons (a hypothetical animal) body colour is either solid white, solid b
ID: 200558 • Letter: 2
Question
2.In griffons (a hypothetical animal) body colour is either solid white, solid black or spotted. Suppose that you crossed a white coated true-breeding griffon with a black coated true breeding griffon and obtained all white F1 progeny. When the F1s are crossed to each other you obtain F2s in the following proportions:
solid white 300
solid black 72
spotted 28
a. Provide an explanation to account for the results. Include genotypes for all the generations.
b. When a solid white griffon from the F2 generation is crossed with a solid black griffon
from the F2 generation the following proportions of progeny are observed:
solid white 8/16
solid black 4/16
spotted 4/16
What are the genotypes of the F2s that were crossed?
Explanation / Answer
F2 progeny:
Solid white = 300
Solid black = 72
Spotted = 28
This corresponds to 12:3:1 phenotypic ratio.
It is dominant epistatic interaction.
Solid white = S_A_ and S_aa
Solid black = ssA_
spotted = ssaa
Parental cross: SsAa X ssAa
Gametes: (SA)(Sa)(sA)(sa) X (sA)(sa)
F1 progeny = SsAA SsAa SsAa Ssaa ssAA ssAa ssAa ssaa
Phenotypic ratio = 2:1:1 = 8:4:4
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