Codominance and incomplete dominance are both types of genetic inheritance patterns that describe how alleles interact in determining the phenotype of an organism.
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Codominance:
- In codominance, both alleles in a gene pair are fully expressed in the phenotype of the organism. Neither allele is dominant or recessive, and the traits associated with both alleles are visible simultaneously.
- A classic example of codominance is seen in the ABO blood group system. Individuals with one allele for A blood type and one for B blood type (genotype AB) express both antigens on the surface of their red blood cells, resulting in the AB blood type.
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Incomplete Dominance:
- Incomplete dominance occurs when neither allele is completely dominant over the other. Instead, the phenotype of the heterozygote (organism with two different alleles) is an intermediate blend of the expressions of the two alleles.
- A common example of incomplete dominance can be found in snapdragon flowers, where crossing a red flower (RR) with a white flower (WW) results in offspring (RW) that are pink, showing an intermediate phenotype rather than one of the parent colors.
In summary:
- Codominance results in both traits being expressed simultaneously (e.g., AB blood type).
- Incomplete dominance results in a blended phenotype (e.g., pink flowers from red and white parents).