Final answer:
Based on the blood types of Jay and Alon, we can conclude that one parent must have a genotype of IAi (type A) and the other IBi (type B) to have children with genotypes ii (O) and IAIB (AB).
Step-by-step explanation:
Jay has type O blood, which corresponds to the genotype ii, and his brother Alon has type AB blood, which corresponds to the genotype IAIB. Given the genotypes of Jay and Alon, we can infer that each parent must have contributed one allele to produce the AB blood type and one allele to produce the O blood type. Therefore, one parent had to be type A or type AO (IA or IAi), and the other had to be type B or type BO (IB or IBi).
A parent with genotype IAi or IBi carries the i allele, which is recessive and necessary to produce offspring with type O blood, like Jay. A parent with IAIB would not be able to produce a child with type O blood since there is no i allele to pass on. Therefore, one parent must have a genotype of IAi and the other must have a genotype of IBi to account for children with genotypes ii (Jay) and IAIB (Alon).