Final answer:
A woman with type A blood has the genotype IAi, which is due to the dominance of the IA allele over the recessive i allele, illustrating codominance in the case of type AB blood where both IA and IB alleles are equally expressed.
Step-by-step explanation:
A woman with type A blood has the alleles IA and i. Her blood type is a result of codominance between the IA allele, which encodes for red blood cells with the A antigen, and the recessive allele i, which does not encode for any antigen. Since IA is dominant to i, the presence of the IA allele determines her blood type as A. However, it is essential to note that in cases where both IA and IB alleles are present, such as in blood type AB, codominance occurs because both antigens are equally expressed on the red blood cells without one overshadowing the other. The ABO blood groups are a classic example of multiple alleles and codominance in human genetics.