Codominance occurs when multiple alleles are expressed at the same time

Codominance occurs when multiple alleles are expressed at the same time.

Codominance occurs when multiple are expressed at the same time.

An example of codominance is blood type. The glycoprotein antigens that make blood types A and B can both be expressed without one "overpowering" the other. In other words, there is no recessive allele here. We call this blood type AB--both the A allele and B allele are expressed.

Contrast this without incomplete dominance. Here, rather than both traits being expressed in full, the traits blend. A flower heterozygous for color with one red allele and one white allele will be pink, rather than white or red, if incomplete dominance is occurring.