Final answer:
Incomplete dominance and codominance describe different genetic situations in which the phenotype of the heterozygote is different from the homozygous phenotypes. In incomplete dominance, the heterozygote exhibits an intermediate phenotype, while in codominance, both alleles are expressed simultaneously in the heterozygote.
Step-by-step explanation:
In genetics, both codominance and incomplete dominance describe situations in which the phenotype of the heterozygote is different from the homozygous phenotypes. In incomplete dominance, the heterozygote exhibits a phenotype that is intermediate between the homozygous phenotypes. An example of this is when red-flowered snapdragons and white-flowered snapdragons produce pink-flowered offspring.
On the other hand, in codominance, both alleles are expressed simultaneously in the heterozygote. A classic example of codominance is the ABO blood groups in humans. The A and B alleles are expressed as A or B molecules on red blood cells, and heterozygotes express both phenotypes equally, resulting in blood type AB.
While incomplete dominance produces an intermediate phenotype, codominance allows for the expression of both phenotypes in the heterozygote. This distinction is important when analyzing the inheritance patterns of different traits.