If the A gene is completely dominant, then the offspring from this cross should display the A phenotype 75% of the time and the a phenotype only 25% of the time. The genotypic ratio however is 1:2:1. There are two heterozygote Aa classes for one homozygous dominant AA class and one homozygous recessive aa class. If the A gene was incompletely dominant so that a mixture of Aa would produce a phenotype intermediate between AA and aa, then the phenotypic ratio would match the genotypic ratio. Both would be 1:2:1. Click on the boxes in the Punnet Square where the intermediate phenotype of the heterozygote would be seen if A were incompletely dominant.