Codominance vs Incomplete Dominance
Incomplete dominance and codominance are words that students encounter in genetics, a field of study of inheritance of traits. These concepts are often very confusing and students fail to appreciate the difference between these two terms. This article will briefly describe the features of incomplete dominance and codominance to make a clearer understanding of these two terms.
In genetic inheritance, for each trait, two different alleles are inherited by the offspring from each parent. One of these alleles is dominant while the other one is recessive. The trait shown up in the offspring is of the dominant allele while the recessive trait remains hidden. For example, if father has brown eyes and mother has blue eyes, the child will get one allele each for eye color from both parents, and since brown color is the dominant allele, it will show up while the blue gene will remain hidden. Genes contain alleles which have genetic sequencing also called DNA sequences. These sequences have information about traits that are passed on from parents to offspring. Each gene has dominant and recessive alleles. It is dominant alleles that show up while recessive alleles remain hidden.
This phenomenon occurs when the alleles received by parents are neither dominant nor recessive but blend together and produce a physical trait that is somewhere in between the two traits. For example, the cross between a plant with red flowers with a plant with white flowers may produce a plant with flowers that are neither white not red but are pink which is a color made by blending red and white together.
Codominance is a similar phenomenon where offspring receives neither dominant nor recessive genes. But instead of a blend of the two, both alleles get mixed up and show in the offspring. In the above example of red and white flowered plants, the offspring may show up white flowers with freckles of red spots which is codominance in the sense that both genes are showing up but neither is dominant.
Examples of codominance and incomplete dominance in human beings
If a child has a father with curly hair and mother with straight hair, he will get a gene for both curly as well as straight hair. If the child has a hair texture that is neither curly nor straight but a wavy one, it is an example of incomplete dominance. This results because both textures blend together to produce an in between texture which is wavy.
Blood groups are another trait where this phenomenon shows up. There are three different genes for blood groups A, B, and O. O is actually a situation where A and B proteins are absent. If a child gets A allele from a parent and B allele from another parent, he will not have a blood group that is a blend of A and B, but rather have a blood type AB which shows both A and B proteins in his blood. This is an example of codominance.
Though incomplete dominance and codominance are similar in nature, they result in totally different traits in offspring which is the major difference between the two.
• Incomplete dominance and codominance are types of inheritance of traits where both alleles are neither dominant nor recessive.
• In incomplete dominance, the resulting trait is a blend of the traits of parents whereas in codominance, both traits show up in the offspring.