Answer:
Explanation:
AB blood group system in humans is determined gene I. This gene has two alleles IA IB. In heterozygous condition, both these alleles both the alleles express completely resulting in a new phenotype. This is called co-dominance and because in this both the alleles are expressed. Thus, in the given question, Sam is with blood group AB⁺ is due to co-dominance because both the alleles A⁺ and B⁺ are codominant with each other.