Blood types Each of us has an ABO blood type, which describes whether two characteristics called A and B are present. Every human being has two blood type alleles (gene forms), one inherited from our mother and one from our father. Each of these alleles can be A, B, or O. The two that we inherit determine our blood type. The table shows what our blood type is for each combination of two alleles.

We inherit each of a parent’s two alleles with probability 0.5. We inherit independently from our mother and father.

Alleles inherited Blood type A and A A A and B AB A and O A B and B B B and O B O and O O

(a) Hannah and Jacob both have alleles A and B.

Diagram the sample space that shows the alleles that their next child could receive. Then give the possible blood types that this child could have, along with the probability for each blood type.

(b) Jennifer has alleles A and O. Jose has alleles A and B. They have two children. What is the probability that at least one of the two children has blood type B? Show your method.