What is the phenotype of an individual who has the genotype IAi?

An individual with the genotype IAi will have a phenotype of blood type A. This is due to the presence of the IA allele, which is responsible for the expression of the A antigen on the surface of red blood cells. The i allele, being the O type allele, does not produce any antigens. Since the IA allele is dominant over i, the presence of one IA allele is sufficient to produce type A blood.

In contrast, the other blood types result from different combinations of alleles. For example, type B would require the presence of the IB allele, type AB necessitates both IA and IB alleles, and type O results only from having two i alleles (ii) which do not express any antigens. Thus, the presence of the IA allele in the genotype clearly indicates that the resulting phenotype will be blood type A.