Trait 2: Co-dominance Co-dominance occurs when there’s more than one dominant allele and they express equally.

Example: Human blood type is co-dominant. IA (type A blood), IB (type B), and i (O blood) are controlled by A and B dominant alleles. If a person inherits A and B alleles, they’ll have AB blood. O blood is caused by two recessive alleles.

Flower Color
(co-dominance) IRIR and IRi = red flowers IWIW and IWi = white flowers IWIR = red/white speckled ii = yellow flowers