Dihybrid Cross. Definition: A dihybrid cross is a breeding experiment between P generation (parental generation) organisms that differ in two traits. The individuals in this type of cross are homozygous for a specific trait. Traits are characteristics that are determined by segments of DNA called genes.
A test cross can determine whether the individual being tested is homozygous dominant (pure bred) or heterozygous dominant (hybrid). Example: To perform an actual test cross with our black guinea pig, we would need a guinea pig (of the opposite sex) that is homozygous recessive (“bb”).