Final answer:
Incomplete dominance reflects one allele more than the other, whereas codominance involves the simultaneous expression of both alleles. Multiple alleles refer to the existence of more than two alleles for a gene.
Step-by-step explanation:
In this scenario, the interaction of a heterozygous pair of alleles in such a way that the phenotype reflects one allele more than the other is known as incomplete dominance. This occurs when the heterozygote exhibits a phenotype that is intermediate between the homozygous phenotypes. For example, when a red-flowered parent and a white-flowered parent produce a pink-flowered offspring.
Codominance, on the other hand, describes the simultaneous expression of both alleles in the heterozygote. An example of codominance is the MN blood groups in humans, where both the M and N alleles are expressed equally in the form of an M or N antigen on red blood cells.
Multiple alleles refer to the existence of more than two alleles of a gene in a population, such as the variations in sizes of pumpkins.