In his experiment with Pea Plant, Mendel crossed pure tall plants (TT) with pure dwarf plants (tt) and he obtained all tall plants in the F1 generation (Tt) which suggested that only one of the traits of parental plant showed in the F1 generation i.e. tall and the other trait- dwarf plants were not obtained.

He crossed these tall plants of F1 generation amongst each other and obtained tall and dwarf plants in the ratio of 3:1 as the second generation (F2 generation). So he observed that the dwarf trait that had disappeared in the F1 generation reappear in the Second generation (F2 generation). Mendel concluded that the traits of dwarf-ness remained hidden in the first generation to re-emerge in the second generation. Thus this shows that the traits may be dominant or recessive wherein, tall traits are dominant and dwarf traits are recessive.