This is best explained in a punnet square, which unfortunatley I cant put on here. I will try to explain it though: if for example T is tall (dominant in this case) and t was short (recessive in this case). If a pure bred tall pea plant (TT) mates with a pure bred short plant (tt). The results of the offspring are all heterozygous tall (Tt) but all have the recessive allele (t). If these offspring are bred together you get: TT (homozygous tall), Tt (heterzygous tall), Tt and tt (homozygous short). This is Mendels experiment. Hopefully it helps
