How is codominance different from incomplete dominance?

Codominance is when both alleles express themselves fully, while incomplete dominance is when the phenotype is a blend of both alleles.

In codominance, both alleles for a gene are expressed equally in the phenotype of the organism. This means that neither allele is dominant or recessive, and the resulting phenotype is a combination of both alleles. For example, in certain breeds of chickens, a black feathered chicken (BB) and a white feathered chicken (WW) can produce offspring with black and white speckled feathers (BW). Here, neither the black nor the white allele is dominant, so both are expressed in the phenotype of the offspring.

On the other hand, incomplete dominance is when the phenotype of the heterozygous genotype is an intermediate of the phenotypes of the homozygous genotypes. This means that neither allele is fully dominant over the other, and the resulting phenotype is a blend of the two. For instance, in snapdragons, a red flower (RR) and a white flower (WW) can produce a pink flower (RW). Here, neither the red nor the white allele is fully dominant, so the phenotype of the offspring is a blend of the two.

In summary, the key difference between codominance and incomplete dominance lies in the way the alleles are expressed in the phenotype. In codominance, both alleles are fully expressed, resulting in a phenotype that shows both traits equally. In contrast, in incomplete dominance, neither allele is fully dominant, resulting in a phenotype that is a blend of the two traits. Understanding these concepts is crucial in the study of genetics, as they provide insight into how traits are passed on from parents to offspring.