Final answer:
A person with A and O alleles will have blood type A, as the A antigen is expressed due to the presence of the IA allele which is dominant over the i allele that leads to the O type.
Step-by-step explanation:
A person who inherits the A and the O blood type alleles will possess the blood type A. This direct answer comes from the understanding that the ABO blood groups are controlled by three alleles: IA, IB, and i. The IA and IB alleles encode for the presence of A and B antigens on the surface of red blood cells, respectively, and are both dominant over the i allele, which does not encode for any antigen and leads to the O blood type.
The alleles IA and IB are co-dominant to each other, meaning if an individual has one of each, they will have an AB blood type. However, when the IA or IB allele is paired with the recessive i allele, the A or B antigen will be expressed respectively, while the O type is not, as it does not produce an antigen. Thus, an individual with an IA and an i allele will have the A antigen on their red blood cells, resulting in a blood type A (genotype IAi). It is also essential to know that individuals with blood type O carry both anti-A and anti-B antibodies, indicating that they must receive type O blood during transfusions to avoid a potentially hazardous immune response.