Codominance and incomplete dominance are both genetic phenomena that describe how alleles express themselves in a phenotype, but they do so in different ways.
Codominance:
- In codominance, both alleles in a heterozygous individual are fully expressed and contribute to the phenotype independently. This means that neither allele is dominant or recessive, resulting in a phenotype that displays characteristics of both alleles simultaneously.
- A common example of codominance is seen in blood type AB, where both A and B alleles are expressed equally.
Incomplete Dominance:
- Incomplete dominance occurs when one allele is not completely dominant over the other. As a result, the heterozygous phenotype is a blend of the two homozygous phenotypes. This blending creates a new phenotype that is different from either parent.
- An example of incomplete dominance can be observed in flower color. When red (RR) and white (WW) snapdragon flowers are crossed, the resulting offspring (RW) are pink, which is a blend of the two parental traits.
Summary:
- Codominance results in both traits being fully and separately expressed (e.g., AB blood type).
- Incomplete dominance results in a blended expression of traits (e.g., pink flowers from red and white parents).