Question

Define the term Codominance.

Answer 1

Hint: Codominance is shown by the AB blood group in humans. In this case, the allelic interaction between the alleles I A and I B is codominant which gives us a new phenotype called AB blood group.

Complete answer:
Co-dominance is a phenomenon that occurs when both the alleles of a gene express themselves or you can say are codominant over each other. In this case, there is no clear distinction between the dominant and recessive alleles. So, we can say that both alleles express themselves simultaneously without being affected by the other allele.

The case of codominance is an exception of Mendel’s first law or The law of dominance.
Examples of codominance include the coat color of animals, AB blood group inheritance, etc.
Let us now understand this better with the help of a cross for the coat color of cows.
We take two parents having coat colors in brown and white. Now when we cross them the offsprings produced have both patches of brown and white on their coats(commonly known as roan). The alleles responsible for brown and white coat both expressed themselves independently thus we say they are codominant.

Note:
- Codominance should not be confused with incomplete dominance. In incomplete dominance, there is a blending of characters to give a phenotype that is intermediate of both the characters i.e. red and white flowered parents will give pink flower offsprings.
- Whereas in the case of codominance, red and white flowered parents will give offsprings that have both red and white color in them i.e. red and white spots.
- The phenomenon of incomplete dominance is shown by the Dog flower (Antirrhinum majus) in the inheritance of the color of the flowers.