Final answer:
Crossing a parent with AO blood type and another with BB blood type can result in an offspring with AB blood type due to the codominance of the IA and IB alleles.
Step-by-step explanation:
Understanding Codominance in Blood Types
When discussing the inheritance of blood types, the ABO blood group system plays a crucial role, which exemplifies a genetic phenomenon known as codominance. For a parent with blood type AO (heterozygous, carrying the IA and i alleles) and another with blood type BB (either homozygous IBI^B or heterozygous IBI), the potential offspring can possess various combinations of these alleles. If the AO parent donates the IA allele and the BB parent donates the IB allele, the offspring would have AB blood type (genotype IAIB), where both the A and B antigens are equally expressed on the surface of red blood cells. This scenario results from the codominance of the IA and IB alleles, each causing the production of distinct antigens on the erythrocytes.
In the case provided, where one parent is AO and the other is BB, offspring with genotype IAIB (blood type AB) are a possible outcome. This demonstrates the concept of codominance, where both IA and IB alleles are equally expressed, as well as multiple alleles in the population (IA, IB, i).