Explanation: The coat of a roan cow consists of both red and white because the two alleles are codominant. Codominance occurs when two alleles outwardly express themselves equally. In codominance, neither of the allele is completely dominant rather they are equally dominant. None is able to mask the effect of the other. The two alleles express themselves equally in the phenotype of the organism. This means that in a roan cow, the allele for white fur is dominant and the allele for red fur is equally dominant, thus they manifested equally as a mixture of both red and white furs.
