When F1 individual (Tt) is crossed with one of the two parents, either tall (TT) or dwarf (tt), such a cross is called the back cross. There are two possibilities in such a cross : -
(i) When F1 (Tt) is crossed with the dominant homozygous (TT) parent, the plants produce will be 100% tall.
(ii) If F1 (Tt) is crossed with recessive homozygous (tt), 50% plants will be tall and 50% dwarf.
Uses of a Back Cross
Back crosses are used by plant breeders to rapidly improve a variety by making a useful trait (gene) homozygous, that is pure.