Incomplete dominance is said to have occurred when offsprings with heterozygous phenotype results from the interaction of two homozygous phenotypes.
For example: A red-colored plant crossed with white-colored plant to give pink-colored offspring shows incomplete dominance.
Also, some flowering plants like Mirabilis Jalapa, Four 'o' clock plants, give offsprings with traits that are intermediate between those of the parents.
Have you ever done a Punnett Square? This question forces you to make one. If your cross a homozygous type A (AA) and homozygous type O (OO) you should get 100% AO. Understanding genetics, an AO gene means a type A blood. Therefore, it's 100% type A blood (AO).
