What type of dominance is shown by the roan color in cattle?

The roan color in cattle is an excellent example of co-dominance, which occurs when both alleles in a heterozygous organism contribute equally and visibly to the organism's phenotype. In the case of roan cattle, the animals typically exhibit a mix of red and white hairs, resulting from one allele coding for red coat color and another coding for white.

Unlike complete dominance, where one allele completely masks the effect of another, co-dominance allows both traits to be expressed simultaneously. Thus, in roan cattle, you can clearly see the influence of both color alleles, leading to the characteristic appearance that is neither fully red nor fully white. This differentiates it from other forms of dominance, such as incomplete dominance, where the phenotype is a blending of traits but does not express both alleles distinctly.

In understanding this, we can recognize that the distinct mix seen in roan cattle reflects the essence of co-dominance perfectly, making it the appropriate choice in this context.