Codominance | Definition & Examples

By | July 27, 2019


Codominance Definition

Codominance is known as the alliance or relationship between two Alleles of Genes at a locus. It is the interaction between two distinct versions of a gene. The organisms or individuals receive one version of a gene (called an allele), from each genetic material of parent.

If both versions of genes (alleles) are different, the domination of one allele expresses, called Dominant Allele, and the other allele effects are masked, called Recessive Allele. In easy words, both alleles are different, then one allele dominants on the other allele.

But in some cases, both allele dominant together and neither allele can mask the effects of other alleles. This phenomenon called Codominance. Codominance occurs when two different traits are both expressed alongside with each other.

Codominant Alleles:

Codominant Alleles descried as multiple alleles (a version of genes) show their effects together at the time. In Codominant Allele, no allele or gene is dominant over other allele or gene, and no allele masked its effect under another allele.

Not all alleles are dominant or no alleles are recessive, infect all alleles express themselves together. When both parents’ alleles are different after breeds both alleles are expressed together in phenotype.

Codominance Examples

  • Blood Type:

Blood type is a common example of Codominance which occurs in blood type of humans. There are three different alleles that appear in our blood cells and help our body to determine the cells of their own. These alleles also said to Blood groups.

These three groups of blood in humans are A, B, and O. The blood group “O” does not have any protein code at all. So, lack of both A and B proteins occur in the people with “O” traits.

The blood groups “A and B” have protein codes. This both protein (alleles), can appear together. If both parents have a different blood group, as one has blood group “A” and other have blood group “B”. Codominance occurs in this phenomenon when both blood groups express together as blood group “AB”.

  • Livestock:

One chicken has white feathers, and another chicken has black feathers. If both chicken breeds with each other, in the result of Codominance, the offspring chicken will have both white and black feathers.

  • Flower Colors:

One flower plant has red petals flower, and another flowering plant has white petals flower. In the result of codominance phenomenon, both different alleles of flower plants produce new flower plant with red and white patches on the petals of the flower.

Because both red and white flowers alleles are dominant along with each other.

  • Sickle Cell Anemia:

Sickle Cell Anemia is a disease, in which red blood cells become thin stretches. If a person has even a single copy of the gene version of sickle cell, then half of their red blood cells become shaped abnormally. Codominance occurs in this phenomenon because of both sickled shaped and normal blood cells mixed with each other and seen in blood.

  • Rhododendron

Rhododendrons and different flowers might also exhibit codominance. In the case of rhododendrons, the crossing of a red and white flower could yield a flower that has collectively both red and white patches.

Many flowers show similar patterns of codominance, wherever collectively both of the parental flower colors show up in several components of the plant.

Incomplete Dominance vs Codominance:

Incomplete Dominance and Codominance both are the two types of inheritance, in which one allele (or a version of a gene) does not completely dominant on another allele. In this phenomenon, one Allele does not mask the effects of other alleles.

Incomplete Dominance occurs when there is a blending of two different alleles, which cause the occurrence of the third phenotype that does not occur in the genetic material of parents.

While, Codominance occurs when both alleles express their effects along with each other in the offspring, and no allele expresses dominant on another allele.

In incomplete dominance, both parents phenotype blends together into new phenotype offspring, while in codominance both parents phonotype show effects together in the offspring.


Incomplete Dominance

  • Codominance is the appearance of both parental phenotypes together in the offspring when a cross is done between individuals with two different phenotypes
  • Incomplete dominance is the appearance of a third Phenotype, which is a combination of both parental Alleles when a cross is done between individuals with two different phenotypes.
  •  The effect of both Alleles is equally Conspicuous
  • The effect of one of the two parental alleles is more conspicuous
  •  Both parental phenotypes are mixed together to form a third phenotype
  • The two parental alleles are not mixed together
  • Both parental alleles produce their effect independently
  •  Effect of the two parental Alleles is intermediate on the Offspring
  •  Both parental alleles can be observed in the offspring
  • Neither parental alleles can be observed in the offspring
  • The qualitative approach of the Gene expression.
  •  The quantitative approach of both Incompletely dominant alleles
  •  Examples include:

Roan character of cows

Inheritance of the AB blood group

  •  Examples include:

Pink Snapdragon,

The inheritance of height, weight & eye  color

Roan Cow:

Roan is a gene, which is the result of Codominant. In roan, each trait is equally expressed. Roan is a coat color which is seen in many animals, such as cattle, horses, and dogs. It defined as the mixture of white and pigmented hairs. The spots gene found on the different locus and can result in completely white roan colored, or solid color animals. Some plants are totally white with some spots on their hairs. Blue Roan, Red Roan, Tan Roan, and Grey Roan, and so on is exist.