In the monohybrid cross, the possible offspring of a cross between two organisms is evaluated, but only one characteristic is taken into account. While in the dihybrid cross two characteristics are evaluated.
However, unlike the monohybrid cross, in the dihybrid cross, combinations of alleles must be made in order to obtain all possible gametes and thus perform the punnet square properly. An example of a dihybrid cross and allele combination is shown in the following image:
Finally, a test cross refers to these two examples. A test cross taking into account only one trait is called a monohybrid cross. A test cross using 2 traits is a dihybrid cross.