Back Cross: When a cross is made between a heterozygous plant (Tt for tall characteristics) and a homozygous parental plant, it is said to be back cross. It is a kind of test cross. With the help of this process the genotype of a plant having unknown characteristics can he identified. For this a cross is made between a plant having unknown characteristics and a plant of same species having homozygous recessive characteristics.
Explanation: When a cross is performed between an unknown (heterozygous) tall pea plant (Tt an) and (to it’s genotype) a homozygous; dwarf (tt) (known genotype) pea plant, the genotype of pea plant can be identified. The back cross is useful in genetics studies for isolating (separating out) certain characteristics in a related group of animals or plants.