Crossing of F hybrid with its homozygous recessive parent is called test cross and the progeny of test cross is called test cross progeny.
A . Monohybrid Test Cross
Thus monohybrid test cross ratio = 1 : 1
B . Dihybrid Test Cross
So dihybrid test cross ratio = 1 : 1 : 1 : 1
C. Trihybrid Test Cross
It involves crossing of a trihybrid (Rr Yy Cc) with triple recessive (rr yy cc). The eight different phenotypes will be obtained in 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1 ratio.
Uses of a Test Cross
The test cross reveals the genotype of an organism displaying the dominant phenotype, hence its name.