What is the term for when both dominant alleles are expressed in an individual?

The term that describes the situation where both dominant alleles are expressed in an individual is codominance. In codominance, neither allele is recessive, and both contribute to the phenotype. This means that in a heterozygous individual, traits from both alleles manifest simultaneously and distinctly. A classic example of codominance is seen in the AB blood type, where both A and B alleles are expressed equally.

Pleiotropy refers to a single gene affecting multiple traits, while epistasis is the interaction between genes where one gene can mask or suppress the expression of another. Variable expressivity involves variations in the phenotype among individuals with the same genotype, leading to differences in trait manifestation despite having the same genetic makeup. Codominance specifically identifies the scenario where both dominant alleles are visibly and equally expressed in the phenotype, making it the correct term for the question asked.