Question

What is codominance? Explain with an example.

Answer 1

This condition is related to the allele expression in the phenotype. This is the only condition where the first law of inheritance proposed by Mendel comes into play- the blending theory. The diploid organisms have two types of alleles on the same gene locus but here the condition arrives when both are expressed either of anyone.

Complete answer:
Co-dominance is a heterozygous condition in which both the alleles of the same gene locus are fully expressed in the phenotype. It is a condition where the recessive gene’s effect is not masked by the dominant one but both are dominant and get expressed as the phenotypic characters.
Both the alleles show an independent effect on the phenotype and hence, they are called Codominant alleles.
Neither of the phenotypes is completely dominant because both of the alleles are expressed hence, it is a mixed expression. It does not matter if the allele is dominant or recessive to each other. If they are capable of producing the protein which can get expressed, it will lead to codominance.

The best example of Codominance is the ABO blood group system. The gene locus is I where three alleles are present A, B, and O. O is recessive to A and B. A and B are codominant to each other. Either of the three getting expressed is normal but when the blood group is found to be AB, then both A and B, get expressed fully.

Note:
Along with co-dominance there is a similar condition that prevails in the offsprings- incomplete dominance. The phenomenon occurs when the alleles are not able to express themselves properly. This results in an intermediate progeny, where offsprings have incomplete phenotypic character, whichever is not expressed.