ABO blood types illustrate what genetic concept?

• A. Incomplete dominance
• B. Codominance
• C. Multiple allele traits
• D. Law of Independent Assortment

Answer: (C)

The trait is governed by more than two alleles at one gene, which is what multiple allele traits are. For ABO blood groups, there are three alleles in the population: IA, IB, and i. Different combinations of these alleles produce the four blood types: IAIA or IAi give type A, IBIB or IBi give type B, IAIB gives type AB, and ii gives type O. This system shows how having multiple alleles at a single locus expands possible phenotypes beyond a simple two-allele switch.

It’s also worth noting that the AB type demonstrates codominance, since both IA and IB are expressed. But the overarching concept illustrated by ABO blood types is the existence of multiple alleles. The law of Independent Assortment isn’t the focus here because this trait is determined by a single gene, and incomplete dominance wouldn’t produce the AB phenotype as seen.