Codominance and its Examples – Imaluop

Hi, we know that different types of gene have different types of molecular form or allele and in a pair of homologous chromosomes the allele determines which expression will show externally and most of the time only one allele among the two allele expresses externally. But sometimes both the alleles express themselves externally together and this condition is known as codominance, it means both the allele become dominant together. 

Basic Idea About Codominance: 

As we discussed earlier, in general case one among the two alleles express externally which is known as dominant but another one hides itself to express outside but in case of codominance the effect of both alleles occurs on the organism equally so all the alleles express themselves together. 

So in codominance one gene never mask the effect of another gene but both the gene show their effect together and we can see many examples in our environment in which different characters express together, for example some plant leaves have various types of pigmented colour and it is possible due to the expression of alleles which responsible for multiple colours. 

Sometimes the codominance creates confusion with incomplete dominance but two are completely different events when in codominance both the allele express together but in case of incomplete dominance an intermediate character of the allele is expressed.

Major differences of codominance with complete dominance and codominance is in case of complete dominance only one allele expresses which another one allele does not express, but in codominance both the allele expresses and in incomplete dominance an intermediate character expressed externally.  

And one more interesting facts about codominance that the expression of the both allele occurs in different part of organisms for example due to codominance different patches of colour can be occur on a leaf but both the colour not mixed together, different colours present on the leaves on different places but in case of incomplete dominance both the colour mix because both the allele express in same part of an organism. 

Examples of Codominance: 

Blood Group Types: 

In humans different types of blood grouping systems are conventional but we will now focus on ABO blood grouping systems as an example of codominance. In humans on their RBC two types of antigen present, antigen A and antigen B and the alleles responsible for antigen A and antigen B show codominance because when both the allele present, both the antigen is produced without masking one allele on another allele.

When both the allele responsible for antigen A and antigen B present in our body then our red blood cells have both types of antigen, antigen A and antigen B and it is responsible for creating the blood group AB so we can say that AB blood group is an example of codominance. 

Colouration in Different Animals: 

Feather colour in different birds like chicken are sometimes governed by expression of codominant gene and due to this reason sometimes we can see different coloured feathers in them.

One another example of codominance in animals is red and white hair colour in cows and the gene responsible for those colours show codominance when they present together and cause both red and white colouration in their body.  

But sometimes it may confuse that the red and white colour are mixed and it can confuse to be incomplete dominance but in actual if we notice a single hair then we will find that either it is red or white so it is not incomplete dominance, it is an example of codominance.  

Rhododendron: 

The flower of rhododendron with white and red coloured patches is also an example of codominance because here the gene responsible for red and white colouration both express simultaneously but never the two colors mix together they appear on different parts of the flower. 

Read More: Chromosomal Theory of Inheritance