The crossing of any of the F1 hybrid or generation back to its homozygous recessive parent only. It is used to test dominance and independent segregation of two genes/application of Mendel’s second law.
Test cross can also be defined as a cross between genetically unknown individual with homozygous recessive individual to determine whether an individual in question is heterozygous for a certain Allele. It can also be used for a test for linkage.