What characterizes the alleles for seed shape in pea plants?

The correct answer highlights that the spherical shape of seeds in pea plants is a dominant trait. In Mendelian genetics, traits are often determined by different alleles, which can be classified as dominant or recessive. In the case of pea plants, the allele for spherical seeds dominates over the allele for wrinkled seeds.

When a pea plant has at least one allele for the spherical seed shape, it will produce spherical seeds. This indicates that the dominant allele masks the effect of the recessive allele (which determines the wrinkled seed shape) in the phenotype of the plant. Consequently, when considering the inheritance patterns in crosses between pea plants, the presence of a single dominant allele for spherical seed shape will ensure that the seed shape manifests as spherical, highlighting how dominance operates in genetic traits.