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leonju
Suppose you have monohybrid snapdragons in your garden and you find that they produce red seeds to white seeds in the ratio of 3:1. If the alleles are designated R (red seeds) and r (white seeds), what are the probable phenotypes of the parents (P1)?
Look at the possible combinations and their outcomes. If even one of the parents is RR, then all the offspring will have at least one dominant red allele - which means they will all be red. This is not what you see. So neither parent can be RR. If both the parents are rr with only recessive alleles, all the offspring will be white. So this is plainly not the case either. If one of the parents is rr and the other is Rr, then half the offspring will be Rr and the other half will be rr. This is not the phenotype ratio you observe either. What option is left...?