Conducting a monohybrid cross of F1 generation plants, the recessive trait reappears in F2 plants in a ratio of 3:1. Let allele A be dominant, and allele a be recessive. Genotypes (and their phenotypes) will be: AA (dominant trait), Aa (dominant trait), aa (recessive trait). In F1 generation, all plants are heterozygotes Aa. After they cross (Aa x Aa), the offspring will be as following: AA (dominant trait), Aa (dominant trait), Aa (dominant trait), and aa (recessive trait). So, there will be 3 plants with dominant traits and one plant with recessive trait.
