Explain codominance taking an example of human blood groups in the population.

Explanation

When two alleles present together in an organism express their trait independently instead of showing dominant recessive relationship, they are called co-dominant alleles and the phenomenon is called codominance Example is ABO blood groups in humans. Four humans blood groups A. B. AB and O are the phenotypes for this trait. The letter A and B refer to the two types of glycoproteins (antigens) coating the Red Blood Cells (RBC) of persons with either type A or type B blood, respectively. Type AB blood contains both the glycoproteins while type O blood contains neither Three different alleles : `I^A I^B` and i a gene determine the phenotypes of the four blood groups. Both `I^A and I^B` are dominant on recessive allele "C. They show their independent dominant effect and produce A and B blood types. When both `I^A`& `I^B` come together, they are both expressed independently in the phenotypes as AB blood group, and are thus said to be co-dominant. A person carries only two out of these three alleles. When a person has two recessive alleles it, it produces 'O' blood group