Incomplete dominance is when the dominant ("R") gene is not completely dominant and cannot fully mask or cover the recessive ("r") gene. This means that it will result in both genes expressing and a mix of traits appearing. In the case of a flower with "R" genes for red and "r" genes for white, the following possibly combinations exist:
RR = all red, no white "r" gene
Rr = pink, as both the "R" and "r" genes are expressed
rr = white, no red "R" gene
The Punnett Square shows that only one of the four phenotypes is RR and red.
