The key difference between codominance and incomplete dominance is based on the expression of the traits in the offspring. In Codominance, the offspring receive a combination of both parent genes, whereas, in Incomplete dominance, neither one of the parent genes expresses.
In genetics, Gregor Mendel discovered the Principal of Dominance. But, it was found that the inheritance of traits takes place due to other non-Mendelian patterns as well. Codominance and Incomplete Dominance are two phenomena that deviate from Mendelian Genetics. Codominance is the phenomenon where the offspring receives both the parent genes as a combination of both the genes. Thus, both the genes express equally in the offspring. In contrast, incomplete dominance is the phenomenon where neither one of the parent genes expresses, instead expresses phenotype, which has a combined effect of both genes.
CONTENTS
1. Overview and Key Difference
2. What is Codominance
3. What is Incomplete Dominance
4. Similarities Between Codominance and Incomplete Dominance
5. Side by Side Comparison – Codominance vs Incomplete Dominance in Tabular Form
6. Summary
What is Codominance?
Codominance is a non-Mendelian inheritance pattern. In this phenomenon, the offspring shares a codominant relationship with the parent-progeny. In Codominance, the offspring receives both parent genes in equal proportions. Both the dominant and the recessive alleles are equally expressed in the offspring. Thus, the alleles simultaneously express in codominance. In codominance, independent expression of alleles occurs, hence, there is no mixing of alleles during the codominance. Furthermore, there is also no quantitative effect on Codominance.
Figure 01: Tabby Cat
The classic example of Codominance is the example of the tabby cat. When pure black cats and brown cats mate with each other, the 1st filial generation will consist of kittens which are black and having brown stripes or spots or vice versa. These kittens are the tabby cats. Codominance can also observe among the Shorthorn cattle.
What is Incomplete Dominance?
Incomplete Dominance is a non-Mendelian inheritance pattern. In this pattern of inheritance, the offspring receives an intermediate trait which is a combination of the parent genes or parent alleles. Therefore, the expression of alleles in the offspring is neither dominant nor recessive. The expressed physical trait is an intermediate trait which is not present in either of the parents. Thus it is a totally new phenotype. Therefore, the expressed allele is of its own. Consequently, the incompletely dominant allele expression can be quantified.
Figure 02: Mirabilis jalapa
The classic example of Mirabilis jalapa flower colour. When completely dominant red flowers cross with white flowers, the resulting progeny consisted of pink flowers. This shows the phenomenon of incomplete dominance.
What are the Similarities Between Codominance and Incomplete Dominance?
- Both belong to the non-Mendelian inheritance patterns.
- In both cases, neither dominant nor the recessive allele is expressed.
What is the Difference Between Codominance and Incomplete Dominance?
Codominance and incomplete dominance are two non-Mendelian inheritance patterns. In codominance, offspring receives a mixture of characteristics of both parental genes irrespective to the dominant and recessive genes. In incomplete dominance, it produces a mixture of both alleles in the offspring. This is the major difference between codominance and incomplete dominance. Further difference between codominance and incomplete dominance is that the effect cannot be quantified in codominance while it can be quantified in incomplete dominance.
The below infographic on difference between codominance and incomplete dominance shows more differences between the two non-Mendelian inheritance patterns.
Summary – Codominance vs Incomplete Dominance
Codominance and Incomplete dominance are two non-Mendelian inheritance patterns. Codominance is the phenomenon where both parental alleles express in the offspring in unequal proportions. In contrast, Incomplete dominance is the phenomenon where an intermediate of both parent alleles expresses in the progeny. Thus, the phenotype of incomplete dominance is unique to the progeny. Codominant effect is not quantifiable, whereas the incomplete dominant effect can be quantified. This summarizes the difference between codominance and incomplete dominance.
Reference:
1.“Multiple Alleles, Incomplete Dominance, and Codominance.” Khan Academy, Khan Academy. Available here
Image Courtesy:
1.”Cat November 2010-1a”By Alvesgaspar – Own work, (CC BY-SA 3.0) via Commons Wikimedia
2.”Gul-Abas-4-O’clock plant”By Khalid Mahmood at English Wikipedia, (Public Domain) via Commons Wikimedia