Codominance/ Incomplete dominance – Check Test

1. One member of a pair of alleles may be equally

dominant to the other and both alleles are fully expressed.

This is called

A complete dominance.

B a dominant cross.

C incomplete dominance.

D codominance

Questions 2 and 3 refer to the following information.

In cattle, the inheritance of coat colour is an example of

incomplete dominance. When a red bull is crossed with a

white cow the offspring is heterozygous.

The red allele has the symbol R.

The white allele has the symbol W.

2. What is the phenotype of a heterozygous cow?

A Red

B RR

C Roan

D RW

3. What is the genotype of a red bull?

A RR

B WW

C RW

D WR

Questions 4,5 and 6 refer to the following information.

The offspring of a cross between a black stallion and a

white mare is a grey roan. The allele for black is B and the allele

for white is W.

4. Which line in the table shows the correct genotypes

for this cross?

	Stallion	Mare	Offspring
A	WW	BB	BW
B	WW	BB	WW
C	BB	WW	BB
D	BB	WW	BW

5. The correct description of the cross involving the genotypes

WW x BW is

A heterozygous x homozygous.

B homozygous x heterozygous.

C heterozygous x heterozygous.

D homozygous x homozygous.

6. The correct description of a cross between two

grey roans is

A heterozygous x homozygous.

B homozygous x heterozygous.

C heterozygous x heterozygous.

D homozygous x homozygous.

Questions 7 and 8 refer to the punnett square for the F₁

generation in a cross involving codominant alleles.

M/F	B	W
W	BW	WW
B	BB	BW

7. What is the genotype ratio in the F₁ generation of this cross?

A 1BB : 2BW : 1WW

B 3BB :1WW

C 1BB : 1BW : 1WW

D 3WW : 1BW

8. What is the phenotype ratio in the F₁ generation of this cross?

A 1 black : 1 white

B 1 black : 2 roan : 1 white

C 3 black : 1 white

D 1 black : 1 roan : 1 white