noun, plural: filial generations
A test cross is the crossing of an organism with dominant genotype to a recessive homozygote for a specific phenotype in order to determine dominance/recessiveness of the unknown genotype and the pattern of inheritance based on the phenotype of each progeny. This was first introduced by Gregor Mendel, an Augustinian monk and botanist, formulated the laws of heredity based on his careful breeding experiments on garden pea plants. His works founded the Mendelian laws that attempts to explain heredity. Because of his seminal contributions, he was duly recognized as the father of genetics. His works were based on a test cross on garden pea plants.
A test cross is made between an organism exhibiting the dominant trait and another organism displaying the recessive trait. The first set of parents in a test cross is referred to as the parental generation (or P-generation). The offspring resulting from a test cross from the P generation are referred to as the filial generation (in this case, first filial generation). The filial generation is marked with the symbol, F. The filial generations are organized in a sequence of matings such that the successive generations after a parental generation is attributed by the symbols F1 (for the first filial generation), F2 (for the second filial generation), etc.