In a dihybrid cross, how many traits do the parents differ by?

In a dihybrid cross, the parents differ by two traits, which is central to understanding this type of genetic cross. A dihybrid cross studies the inheritance of two different genes, each of which has two alleles. For instance, if we are considering traits such as seed shape (round vs. wrinkled) and seed color (yellow vs. green) in pea plants, the parents would have different combinations of these two traits.

When performing a dihybrid cross, we can examine how these traits are inherited independently of each other, following Mendel's law of independent assortment. This allows for the generation of various genotype combinations in the offspring, specifically a 9:3:3:1 phenotypic ratio in the F2 generation, which highlights the diversity that can arise from the combination of two different traits. Hence, "two traits" accurately describes the basis of a dihybrid cross.