The combinations resulting from a genetic cross may be predicted by using a Punnett square. One-fourth of the plants with two alleles for purple flowers. One-half of the plants with one allele for purple flowers and one allele for white flowers. Since the purple-flower allele is dominant, these plants have purple flowers. One-fourth of the plants with two alleles for white flower color, which will have white flowers since no dominant allele is present.
All gametes carry that allele.
Homozygotes are true-breeding. Heterozygotes are not true-breeding. Because some alleles are dominant over others, the genotype of an organism may not be apparent. The breeding of an organism of unknown genotype with a homozygous recessive. By the law of independent assortment, each pair of alleles segregates into gametes independently Mendel deduced the law of segregation from experiments with monohybrid crosses, breeding experiments that used parental varieties differing in a single trait.