Why test cross is called back cross?

Test cross:

1. It is the cross between an individual of dominant phenotype but unknown genotype with a individual of homozygous and recessive genotype as well as phenotype.
2. It helps in determining whether the organism is homozygous or heterozygous.
3. Homozygous individuals have two copies of same alleles such as TT or tt whereas heterozygous individuals have one copy of two different alleles such as Tt.

Back cross:

1. The cross of a hybrid organism with one of its parent or an individual genetically similar to the parent.
2. Back cross is done to obtain genetically similar offsprings as that of the parents.

Test cross is also called a back cross because:

1. In a test cross F1 generation that has a dominant phenotype is crossed with a parent plant that has homozygous recessive genotype or recessive phenotype.
2. Since, the cross is done with the parent individual, it can be considered as a back cross.