So we’ll just use “R” and “r” for this example. If the mother AND father are heterozygous, then both of their genotypes are “Rr” if you work out the lumber square or use the foil method, the box would look like this: RR on top left, Rr on top right, Rr on bottom left, and rr on bottom right. So the genetic probabilities, using four as the sum would be 1:2:1
