When Mendel first crossed pure tall pea plants with pure dwarf pea plants, he found that only tall plants were produced in the first generation(F1 generation). No dwarf pea plants were obtained in the first-generation of progeny. When F1 tall plants were self-pollinated, Mendel got both tall and dwarf plants in F2 generation in 3 : 1 ratio. In other words, in the F2 generation three-fourth plants were tall and one-fourth were dwarf. Mendel called this t.all character as dominant trait and dwarf character as recessive trait.
