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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. The term is sometimes written with a subscript, as F1 hybrid.
All F1-hybrid plants have the genotype S s and all are spherical (dominant characteristic). The recessive alleles segregate during gamete formation. As a result, one out of four possible combinations of F2-generation plants will have the homozygous recessive genotype (ss).ll of the gametes of the spherical seeded parent have the S (dominant) allele and all of the gametes of the dented seeded parent have the s (recessive) allele. All of the F1 generation plants will have the genotype of S s (heterozygous), and all will be spherical seeded.