A test cross in genetics is a way to determine whether an individual possessing a dominant phenotype has a homozygous dominant (two dominant alleles) or heterozygous dominant (one dominant and one recessive allele) genotype. For example, in pea plants, purple color is dominant and white color is recessive. If a pea plant has purple flowers, it could have the homozygous dominant genotype (its offspring with a white-flowered plant will have purple flowers only) or the heterozygous genotype (the flower may have about half/half purple and white offspring with a white-flowered plant).