Question

a roan cow shows co - dominance in fur color (orange and white). what is the phenotype ratio expected if a roan cow and a roan steer mate together?

1. orange: 2 orange and white: 1 white

2 orange: 2 orange and white: 0 white
4: orange and white
1: orange : 1 white

Explanation:

Step1: Define co-dominant alleles

Let $O$ = orange allele, $W$ = white allele. Roan = $OW$ (co-dominant, both traits show).

Step2: Set up parental genotypes

Roan cow: $OW$, Roan steer: $OW$.

Step3: Create Punnett square

$$\begin{array}{c|cc} & O & W \\ \hline O & OO & OW \\ W & OW & WW \\ \end{array}$$

Step4: Count phenotypes

• $OO$ (orange): 1
• $OW$ (roan/orange-white): 2
• $WW$ (white): 1

Step5: State phenotype ratio

Ratio: 1 Orange : 2 Orange and White : 1 White

Answer:

1: Orange: 2 Orange and White: 1 White