Codominance and incomplete dominance are the two types of dominance in genetics. These two types of processes contain alleles that are not dominant and are not recessive. The difference between them usually shows on the appearances as the carried trait. In incomplete dominance, the traits occur simultaneously as one in the offspring; while in codominance, the traits are also produced together at the same time. Now, what makes them different from each other?
It is simply that in incomplete dominance, the mixture of alleles is experienced as a trait; while in codominance, the alleles also exist at the same time but not as a trait. Actually, incomplete dominance usually exists in human beings or animals, while codominance usually occurs in plants. For example, the mating of a man with curly hair and a woman with straight hair producing an offspring with wavy hair is an example of incomplete dominance. A yellow flower and green leaves combining with another yellow flower and red leaves producing a yellow flower with red and green leaves side by side is an example of codominance.
The significant difference between codominance and incomplete dominance is based upon the expression of the qualities in the progenies. In codominance, the children receive a combination of both parent genes. Both genes express equally in the offspring. It is when both alleles are similarly strong, and both alleles are visible in the hybrid genotype. An example would be if a white chicken is crossed with a black chicken. With codominance, the chicken would not come out grey, but it would possess both black and white feathers.
With incomplete dominance, a dominant allele, or form of the gene does not entirely mask the effects of the recessive allele. In other words, there are two different parent genes, but the child comes out with the genes blended. For example, a child who has one parent with curly hair, and the other parent has straight hair; incomplete dominance is demonstrated through the child having wavy hair.
When an animal receives both parent genes, and they are in equal proportions, then this is considered to be codominance. When an animal receives a trait from their parents, but it is from a combination of alleles and genes from the parents, then this is considered to be incomplete dominance. Both are non-Mendelian inheritance patterns. In codominance, there is an independent effect of the hybrid, whereas, in incomplete dominance, there is an intermediate of the two alleles of the hybrid.
In codominance, both alleles are conspicuous equally, whereas one allele is conspicuous more than another in the incomplete dominance. The quantitative effect in codominance is absent, whereas the quantitative effect in incomplete dominance is present. These two patterns have a few similarities and differences.