

For the F2 generation of a monohybrid cross, three possible combinations of genotypes could occur: homozygous dominant, heterozygous, or homozygous recessive. Heterozygotes can arise from two different pathways (receiving one dominant and one recessive allele from either parent), and because heterozygotes and homozygous dominant individuals are phenotypically identical, the law supports Mendel s observed 3:1 phenotypic ratio.
