Which blood type is an example of codominance?

In genetics, codominance occurs when two different alleles are expressed simultaneously in a heterozygote, resulting in a phenotype that displays both traits equally. Blood type AB is a prime example of codominance because it contains both A and B alleles. When an individual inherits an A allele from one parent and a B allele from the other, both blood group characteristics are fully expressed, leading to the AB blood type.

With blood type A and blood type B, these types represent scenarios where one allele is dominant over the other when paired with type O. Blood type O is considered recessive and does not express A or B antigens, therefore it does not demonstrate codominance either. Blood type AB, however, showcases how both alleles can manifest together because they are equally dominant when present. This is a key aspect in understanding blood types and their inheritance, particularly in transfusion compatibility and genetics.