Question

Conceptual Questions: Answer as short and concise as you can, but make sure you have all of the needed detail that indicates to me you know the answer. Do not assume I know what you are talking about and explain it to me. When I state you need to show your work, you can do the calculations on a separate sheet of paper and then type the calculations out. It is not that difficult

You are studying a unique coloring pattern in hamsters and after mating the two dihybrids you notice an interesting phenotypic ratio of 9:6:1 in the F₂ progeny. You decide it's a variation of the 9:3:3:1 ratio. (12 Points)

You are studying a unique coloring pattern in hamsters and after mating the two dihybrids you notice an interesting phenotypic ratio of 9:6:1 in the F₂ progeny. You decide it's a variation of the 9:3:3:1 ratio. (18 Points)

(a) What is a potential explanation for this phenomenon?

(b) Using the alleles 'A' and 'B' for the dominant alleles, show the expected genotypes that would be expected from the 9:6:1 ratio?

(c) Because there is ambiguity in the some of the genotypes (a hint to part (b)), how would you go about testing your predictions.

Answer 1

a).

9:6:1 ratio is a result of duplicate genes with cumulative effect mode of epistasis.

Certain phenotypic traits depend on the dominant alleles of two gene loci. When dominant is present it will show its phenotype. The ratio will be 9: 6: 1.

A_B_ = Phenotype 1

A_bb or aaBB = Phentype 2

aabb = Phenotype 3

b&c).

AaBb x AaBb ---Parents

Aa x Aa = A_ (3/4) & aa (1/4)

Bb x Bb = Bb (3/4) & bb (1/4)

Phenotype 1 = A_B_ = 3/4 * 3/4 = 9/16

Phenotype 2 = A_bb + aaB_ = 3/4 * 1/4 + 1/4 * 3/4 = 6/16

Phenotype 3 = aabb = 1/4 * 1/4 = 1/16