In rabbits, albinism is an autosomal recessive condition caused by the absence o

ID: 218589 • Letter: I

Question

In rabbits, albinism is an autosomal recessive condition caused by the absence of the pigment melanin from skin and fur. Pigmentation is a dominant wild-type trait. Three pure-breeding strains of albino rabbits, identified as strains 1, 2, and 3, are crossed to one another. In the table, F1 and F2 progeny are shown for each cross.

Based on the available data, propose a genetic explaination for these results. Choose the correct mutiple choice.

A) 2 genes, complementary gene action

B) 1 gene, simple dominance

C) 2 genes, dominant epistasis

D) 2 genes, recessive epistasis

E)1 gene, codominance

Cross Strains F1 Progeny F2 Progeny A 1 × 2 56 albino 192 albino B 1 × 3 72 pigmented 181 pigmented, 139 albino C 2 × 3 34 pigmented 89 pigmented, 72 albino

Explanation / Answer

Answer:

A) 2 genes, complementary gene action

Cross

Strains

F1 Progeny

F2 Progeny

1 (aabb)× 2 (aabb)

56 albino (aabb)

192 albino (aabb)

1(aabb) × 3(AABB)

72 pigmented (AaBb)

181 pigmented(A_B_), 139 albino (A_bb or aaB_ or aabb)

2(aabb) × 3(AABB)

34 pigmented (AaBb)

89 pigmented (A_B_), 72 albino (A_bb or aaB_ or aabb)

Explanation:

181:139 = 9:7

89:72 = 9:7

9:7 ratio is caused by the duplicate recessive epistasis.

A_B_ = Pigmented

A_bb or aaB_ or aabb = Albino