Question

1. Given the following scenario, what would be the phenotypic outcome of this dihybrid cross for the F2 generation:

	A) 4 birds with yellow/normal wings: 4 birds with yellow/clear wings: 4 birds with white normal wings: 4 birds with white/clear wings
	B) 16 birds with yellow/normal wings
	C) 9 birds with yellow/normal wings: 3 birds with yellow/clear wings: 3 birds with white normal wings: 1 bird with white/clear wings
	D) 8 birds with yellow/normal wings: 8 birds with white/clear wings

2. Given the following scenario, how many birds in the F2 generation would be homozygous recessive for the clear wing trait?

	A) 8
	B) 4
	C) 3
	D) 1

3. Given the following scenario, how many of the birds in the F2 generation would be heterozygous for both traits:

	A) 8
	B) 2
	C) 3
	D) 4

Answer 1

Answer:

1).

C) 9 birds with yellow/normal wings: 3 birds with yellow/clear wings: 3 birds with white normal wings: 1 bird with white/clear wings

Explanation:

F2 phenotypic ratio of Dihybrid cross is 9:3:3:1

2). B). 4

Explanation:

A= Yellow; a = white

B= Normal wing; b = Clear wing

AaBb x AaBb –Dihbrid cross

	AB	Ab	aB	ab
AB	AABB (yellow, normal wing)	AABb (yellow, normal wing)	AaBB (yellow, normal wing)	AaBb (yellow, normal wing)
Ab	AABb (yellow, normal wing)	AAbb (yellow, clear wing)	AaBb (yellow, normal wing)	Aabb (yellow, clear wing)
aB	AaBB (yellow, normal wing)	AaBb (yellow, normal wing)	aaBB (white, normal wing)	aaBb (white, normal wing)
ab	AaBb (yellow, normal wing)	Aabb (yellow, clear wing)	aaBb (white, normal wing)	aabb (white, clear wing)

Clerar wing = AAbb (1) + Aabb (2) + aabb (1) = 4

3). D. 4

Explanation:

AaBb = 4