Part 3: Codominance w e
There is another kind of inheritance that is neither based on the dominant allele type nor the incomplete-dominant
type. Remember the word that characterized incomplete dominance: blend. However, what if the result was not a
blending of the two types? What if, instead, it was a mixture in which both traits showed up? Consider this case.
In horses there is a single gene system that controls the color of the horse's coat. This system has two alleles;
let's call these alleles L and L', or L prime.
A horse that is LL will have red hair.
A horse that has L'L' will have white hair.
A horse that has LL' will have BOTH red and white hairs intermixed. A horse like that is called a roan.
This phenomenon is called codominance.
6. Draw a Punnett square to determine the outcome of a cross between two roan horses.

7. What is the ratio of coat colors that will result from this cross?