Question

when one allele is not dominant over the other, resulting in both traits expressed in a heterozygous individual..... codominance incomplete dominance

Explanation:

The definition describes a scenario where both alleles in a heterozygous individual are fully expressed, rather than blending or one masking the other. This matches the core characteristic of codominance, whereas incomplete dominance results in a blended phenotype.

Answer:

Codominance