Genetics is an excellent division of biology where we study the different features and functions of genes. The natural phenomenon where the genes dominate other genes of similar properties is called dominance. When two different genes exhibit different characteristics of a similar property it is called codominance. In this section, we will study this natural phenomenon with examples and learn how the codominant alleles exhibit such property. This property of the alleles can be seen across the flora and fauna of our ecosystem.
What is Dominance?
To understand the meaning of codominance, we will have to learn what dominance is. As per the genetic explanation of different physical features of a plant or animal, there are two or more types of genes for the expression of a particular feature. For the sake of discussion, let us consider two characteristics for a particular feature. Every character is expressed by a particular gene or allele. When the parent generation contains both the characters, the genes are passed to the offspring. It has been found that only one of the characteristics will be expressed and the other one will be suppressed.
The characteristic that was expressed is called dominant and the suppressed one is called recessive. It means that the dominant gene suppressed the recessive gene and expressed its format. This is called dominance. Let us proceed to understand the phenomenon of codominance.
What is Codominance?
As the name suggests, we can easily understand the meaning of this biological term now. It is the natural phenomenon where the two or more characteristics of a particular feature will get expressed in the offspring. It means that all the genes of this same feature will express themselves reflecting in the formation of visible characteristics. This is called codominance.
As per the law of codominance, it is the unique relationship between two genes where both the genes exhibit and express their properties simultaneously. It also means that the offspring will exhibit the same physical properties that its mother and father have. If we consider an example, we will easily understand its technical meaning and explain codominance.
When a brown cow is mated with a white bull, the offspring can either be white or brown. If this happens then it is an example of dominance. If the offspring is white, the dominant gene from its father has expressed its trait. If it is brown then it has got the dominant gene from the mother. If both the colours exist simultaneously then this is the case of codominance. Both the genes are considered to be codominant alleles as they have not suppressed the other and have collaboratively expressed their characteristics. This is a natural phenomenon that happens in the field of inheritance of genetic features.
Codominant inheritance can be witnessed in plants and animals. You might have seen flowers with a mixed colour pattern. The same plant produces flowers of different colours. When a flower has a single colour, it is an example of dominance. When the flowers have multiple colours, it means that the genes responsible for the colours have acted co-dominantly. They all have expressed their colours in a flower.
What is Incomplete Dominance?
Another term closely related to codominance in the subject of inheritance is incomplete dominance. This is a natural phenomenon where the traits of the parental generation are expressed together forming a new hybrid trait. For instance, the expression of the multiple alleles during the hybridization of a yellow-flowered plant and a red-flowered plant will give birth to an orange-flowered plant.
In this example, you can easily understand the difference between codominance and incomplete dominance. If it was a codominant trait expression, the flower would have both yellow and red colours present at the same time. When it has produced a new colour, it is because of the incomplete dominance of both the responsible alleles. Both the genes of red and yellow colour incompletely expressed themselves to give birth to a new orange colour.
Examples of Codominance
The best example, in this case, is the codominance blood type. ABO group is considered to be a codominant blood group where both father’s and mother’s blood group is expressed. It means that the properties of the blood groups exist in the ABO type. The offspring are carrying the traits of both blood groups of their parents.
It can also be seen in cows, dogs, etc. The puppies and calves develop different fur colours when it comes to the parents. It means that the phenotype ratio will not be similar to the dominant one. As per the codominance genetics, the 1:2:1 ratio in dominance phenotype will not exist.
This article has explained what codominance is and how it occurs naturally. The examples are given for a proper explanation of the inherited traits. You can also understand the difference between incomplete and codominance properly by referring to those examples. Understand how the alleles function and realize how the codominant blood group appears in a progeny. We also saw the difference between dominance and incomplete dominance with proper examples and the difference between codominance and incomplete dominance.