In a plant, a single locus affects both berry color and berry size. There are two mutant alleles (R1 and R2) in addition to the wild-type allele (R0). Individuals that are R0R0 have large, white berries. Individuals that are R1R1 or R0R1 have red berries, individuals that are R2R2 or R0R2 have small berries, and R1R2 individuals have berries that are both red and small. Thus...R1 is dominant to R2.R2 is dominant to R1.R1 and R2 exhibit incomplete dominance.R1 and R2 exhibit codominance.R1 and R2 exhibit pleiotropy.

In the given plant, pleiotropic locus regulates both berry color and berry size. The R1 allele gives red berries while the R0 allele is responsible for white berries. The heterozygote R0R1 also has red berries, which means that R1 is dominant over R0 for the color of berries. The R2 allele is responsible for the "small" size of berries in homozygous genotype.

The genotype R0R2 also has small berries, which means that R2 is also dominant to R0. However, the genotype R1R2 imparts red color and small size to berries. In the genotype R1R2, both the R1 (responsible for the red color of berries) and R2 (responsible for the small size of berries) alleles are expressed. This represents the fact that the R1 and R2 alleles are codominant and express themselves in heterozygous R1R2 genotype.