Which of the following genetic inheritance patterns is exemplified by human ABO blood group systems, where both alleles A and B express themselves fully and equally when present together?

💡 Solution & Explanation

Codominance occurs when two different alleles at a locus are both fully expressed in the heterozygous phenotype, as seen in human AB blood groups where alleles IA and IB produce both A and B antigens on red blood cells. Incomplete dominance results in an intermediate blended phenotype, polygenic inheritance involves multiple genes contributing to continuous traits like skin color, and sex-linked traits are carried on sex chromosomes like the X chromosome.