The above examples involved a single gene only, and a single set of alleles. But, what if TWO different genes are involved. Well, that makes the crosses more complicated and we term this a dihybrid cross . As long as the genes are on separate chromosomes, things go pretty easily. As you will note below, all offspring are AaBb and will possess the same phenotype.
Lets say each of the genes involves complete dominance and recessiveness.
Thus, AA and Aa encode a red phenotype, and aa represents white. Lets also say that BB and Bb are hairy, whereas bb is bald. Anytime you perform a dihybrid cross, work with two totally heterozygous individuals, and if the alleles exhibit dominance and recessiveness, then you will end up with these same genotypic and phenotypic ratios. One thing that you should notice about the dihybrid crosses is that each pair of alleles of a gene behaves independent of the pair of alleles for the other gene. When Mendel performed his dihybrid crosses, he noticed this as well.