Final answer:
If both parents are heterozygous for the seed shape gene, the offspring can have three possible genotypes: NNSs, NnSs, and nnSs. The first two genotypes would result in all smooth seeds, while the third genotype would result in a 1:1 ratio of smooth to wrinkled seeds.
Step-by-step explanation:
In pea plants, smooth seeds (S) are dominant to wrinkled seeds (s).
If both parents are heterozygous for the seed shape gene (N smooth, n wrinkled), there are three possible genotypes for the offspring: NNSs, NnSs, and nnSs.
The first genotype (NNSs) would result in all smooth seeds.
The second genotype (NnSs) would also result in all smooth seeds.
The third genotype (nnSs) would result in a 1:1 ratio of smooth to wrinkled seeds.