What is the Definition of First filial generation, or F1 generation?

An F1 hybrid (or filial 1 hybrid) is the first filial generation of offspring of distinctly different parental types. F1 hybrids are used in genetics, and in selective breeding, where it may appear as F1 crossbreed. In other words, The filial generation comprised of offspring (s) resulting from a cross between two individuals from parental generation. In genetics, a test cross is a cross involving two individuals in order to determine zygosity (i. e. the degree of similarity of the alleles for a trait in an organism). For instance, a test cross is done 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 parental cross are referred to as the first filial generation (or F1 generation). The F1 generation is the generation resulting immediately from a cross of the first set of parents (parental generation).

A particular example is a cross between two garden pea plants, i. e. one plant producing purple flowers and another plant producing white flowers as performed by Gregor Mendel (the Father of Genetics). These two plants comprise the parental generation (P generation) and the first hybrid offspring from the parental cross comprise the first filial generation. In Gregor Mendel's test cross, the F1 offspring produce purple flowers. When the F1 hybrids were allowed to self-pollinate, the offspring resulted in plants producing either purple or white flowers. The offspring from the F1 generation comprise the second filial generation or F2 generation.