In a pea plant for example, starch synthesis is controlled by one gene. It has two alleles B and b. What must be the phenotype of pea plant with the genotype Bb?

Gene B of pea not only affects the phenotype of pea seed shape but also size of starch grains. It is a pleiotropic gene. In terms of shape of seed, it shows dominance pattern of inheritance and in case of size of starch grains, it shows incomplete dominance pattern of inheritance. Hence in heterozygous condition, the seeds are round but its starch grains have medium size.