Question

Blood type is a classic example of codominance. Why?

A. Both alleles contribute to the phenotype.

B. Only the dominant allele contributes to the genotype.

C. Only the recessive allele contributes to the genotype.

D. Multiple genes contribute to a person's blood type.

Answer 1

In the ABO blood group system, the IA and IB alleles are codominant, meaning both contribute to the phenotype, making blood type a classic example of codominance.

Step-by-step explanation:

Blood type is often used to demonstrate codominance because in the ABO blood group system, both alleles contribute to the phenotype of the organism when they are different. For example, the alleles IA and IB are codominant. If a person inherits the IA allele from one parent and the IB allele from the other, the person will express both enzymes that add A and B antigens to the surface of their red blood cells, therefore having blood type AB. The allele i is recessive and does not produce any surface antigen, leading to blood type O if both alleles are i (ii). The correct answer to why blood type is an example of codominance is A. Both alleles contribute to the phenotype.