What is true about codominance?

Codominance refers to a genetic scenario where both alleles in a heterozygous individual are fully expressed, leading to a phenotype that displays both traits distinctly. This is different from incomplete dominance, where the traits may blend together, or from dominance, where only one allele's trait is expressed while the other is masked.

A classic example of codominance can be seen in the ABO blood group system, where individuals with the genotype IAIB express both A and B antigens on the surface of their red blood cells, clearly displaying features from both alleles.

The concept does not relate exclusively to recessive traits; rather, it is about the simultaneous expression of both alleles in a heterozygote, which showcases their phenotypic effects equally without one overshadowing the other. Understanding codominance is essential for studying inheritance patterns and predicting phenotypes in offspring based on parental genotypes.