The expression of a trait in both the homozygous and the heterozygous condition. In experiments with the garden pea, the Austrian botanist Gregor Mendel crossed plants from true-breeding strains containing contrasting sets of characters. For seed shape, round and wrinkled strains were used. When plants with round seeds were crossed to plants with wrinkled seeds (P₁ generation), all offspring had round seeds. When the offspring (F₁ generation) were self-crossed, 5474 of the resulting F₂ offspring were round and 1850 were wrinkled. Thus, the round trait is expressed in both the F₁ and F₂ generations, while the wrinkled trait is not expressed in the F₁ but is reexpressed in the F₂ in about one-fourth of the offspring. In reporting these results in a paper published in 1866, Mendel called the trait which is expressed in the F₁ generation a dominant trait, while the trait which is unexpressed in the F₁ but reappears in the F₂ generation was called a recessive trait.