Pure tall plants are crossed with pure dwarf plants. In the F ₁ generation, all plants were tall. These tall plants of F₁ generation were selfed and the ratio of tall to dwarf plants obtained was 3: 1 . This is called

Step-by-step solution

The phenotype produced by heterozygotes is identical with that produced by homozygous for the concerned dominant allele. The dominant allele in such a situation is known as completely dominant, eg, when pure tall plant is crossed with pure dwarf plant. In F₁ generation, all plants were tall. These tall plants of F ₁ generation were selfed than the ratio of tall to dwarf plants obtained was 3: 1 . So, allele of tallness is dominant to allele of dwarfness.