In shorthorn cattle, when a red bull (R R) is crossed with a white cow (W W), all the offspring are roan—a spotted, red and white color.

What genotypes are expected from mating a roan bull and a roan cow?

RR, RW, RW, WW

Explanation:

This is an example of codominance, in which both alleles for a trait are expressed in the offspring. Do not confuse this with incomplete dominance in which the alleles blend; otherwise, the roan would have been pink. By crossing a red bull and white cow, we get the genotype of RW for a roan. This will be the genotype of all offspring.

What happens if you cross an RW with an RW? You get RR, RW, RW, and WW; in other words, you get 1 red, 2 roan, and 1 white offspring.

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