Difference Between Codominance, Incomplete Dominance and Dominance
Genetics is a magnificent division of science where we concentrate on the various elements and elements of genes. The normal peculiarity where the genes overwhelm different genes of comparative properties is called predominance. At the point when two unique genes show various attributes of comparable property, it is called codominance. In this segment, we will concentrate on this regular peculiarity with models and figure out how the codominant alleles display such property. This property of the alleles should be visible across the vegetation of our environment.
What is meant by Dominance?
To move forward to codominance, we will have to first decode it and know the meaning of dominance. According to the genetic clarification of various actual highlights of a plant or creature, there are at least two kinds of genes for the declaration of a specific element. For conversation, let us think about two qualities for a specific element. Each character is communicated by a specific quality or allele. At the point when the parentage contains both the characters, the genes are passed to posterity. It has been observed that just one of the qualities will be communicated and the other one will be smothered. Two terms are related to dominance and that affect the cause and effect of its relationship. Those terms are given below:
Dominant - It is the characteristic that was expressed in the above explanation.
Recessive - The other suppressed characteristic is known as the recessive.
The dominant gene is supposed to suppress the recessive gene and hence the process is completed. This whole process of suppressing and repressing is known as dominance. Now, let us get to the understanding of codominance.
Meaning of Codominance
Codominance is a natural phenomenon in which at least two characteristics are involved together of a particular feature get expressed into an offspring. It explains that the same features will express themselves in all genes, reflecting in the building of visible character. This is a complex phenomenon, hence known as codominance. Coming so far now we can understand this complicated phenomenon that we see everywhere but could not notice.
The law of codominance proves that there is a unique relationship between a minimum of two genes where they both express and exhibit their properties simultaneously. It also defies that an offspring will have both physical and psychological properties of its father and mother.
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 the dominance phenotype will not exist.
Conclusion
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.
FAQs on Codominance
1. What is codominance? Explain with a classic example.
Codominance is a pattern of inheritance where two different alleles for a single gene are both fully and independently expressed in the phenotype of a heterozygous individual. Neither allele masks the other. A classic example is the roan coat colour in cattle. If a red-coated parent (RR) is crossed with a white-coated parent (WW), the heterozygous offspring (RW) will have a roan coat, which consists of a mixture of both red hairs and white hairs, not a blended pink colour.
2. What is the key difference between codominance and incomplete dominance?
The main difference lies in how the alleles are expressed in a heterozygote:
- In codominance, both alleles are expressed separately and distinctly. For example, a flower with alleles for red and white colours would have patches of red and patches of white.
- In incomplete dominance, the alleles blend to create a new, intermediate phenotype. The same flower would appear pink, as neither the red nor the white allele is fully dominant.
3. How is the human ABO blood group system an example of codominance?
The ABO blood group system in humans is a prime example of codominance involving the alleles IA and IB. An individual who inherits the allele IA from one parent and IB from the other will have the blood type AB. This is because both alleles are expressed simultaneously, resulting in the production of both A-type and B-type antigens on the surface of their red blood cells. Neither allele is recessive to the other.
4. How does the expression of alleles differ in codominance versus simple Mendelian dominance?
In simple Mendelian dominance, a heterozygous individual expresses only the trait of the dominant allele, while the trait of the recessive allele is completely masked. In contrast, in codominance, a heterozygous individual expresses the traits of both alleles simultaneously and without any blending. Both parental phenotypes can be observed side-by-side in the offspring.
5. Can a single gene exhibit both codominance and multiple alleles? Explain.
Yes, a single gene can exhibit both phenomena. The best example is the human ABO blood group. This system is controlled by three alleles (IA, IB, and i), which is an instance of multiple allelism. Within this system, the alleles IA and IB are codominant to each other, as they are both expressed in an individual with the AB blood type. Both alleles are, however, dominant over the 'i' allele.
6. What is the expected phenotypic ratio in a monohybrid cross involving codominant alleles?
In a monohybrid cross between two heterozygous individuals involving codominant alleles (e.g., RW x RW), the expected phenotypic ratio is 1:2:1. This is because each genotype has a unique phenotype:
- 1 Homozygous (e.g., RR - Red)
- 2 Heterozygous (e.g., RW - Roan)
- 1 Homozygous (e.g., WW - White)
This differs from a simple dominant-recessive cross, where the phenotypic ratio is 3:1 because the heterozygous individuals display the same phenotype as the homozygous dominant individuals.
7. If both parental traits appear in codominance, does this result in a 'blended' intermediate phenotype?
No, this is a common misconception. A blended or intermediate phenotype is the hallmark of incomplete dominance (e.g., red and white parents producing pink offspring). In codominance, both parental traits appear distinctly and separately in the offspring. For instance, in a flower exhibiting codominance, you would see separate patches of red and white, not a uniform pink colour.
