In this example of gene interaction, both gene pairs influence fruit shape equally. When a summer squash with disc-shaped fruit (AABB) are crossed with plants with long fruit (aabb), the heterozygous F₁ all have disc fruit.

However, in the F₂ progeny, some individuals show a novel shape, sphere, if it possesses a dominant allele at either locus.

In the absence of dominant alleles, the fruit is long. if both dominant alleles are present, the fruit is flattened into a disc shape.