Co-dominance occurs when both alleles in a heterozygous genotype for a trait are both equally expressed. An example is the human AB blood group, in which both the A and B alleles are equally expressed.
Incomplete dominance occurs when the heterozygous genotype for a trait is expressed as a blend. An example is blue feather color in chickens, in which a black allele and white allele together are expressed as blue feather color.
