Question

What would be the expected outcome if you performed a testcross with a roan cattle (RW) using a white cattle (WW)?

Options

• All roan cattle

• 1 Red : 1 Roan : 1 White

• All white cattle

• 1 Roan (RW) : 1 White (WW)

Answer 1

In a testcross between roan cattle (RW) and white cattle (WW), the white parent can only produce W gametes while the roan parent can produce either R or W gametes with equal probability. The offspring genotypes will be 50% RW (roan) and 50% WW (white), producing a 1:1 phenotypic ratio. This ratio is characteristic of a testcross involving co-dominant alleles and is useful for determining the genotype of an individual with the dominant phenotype.