Question

prisha knows her blood type is a, but sebastian does not know his blood type. however, sebastian knows that his mother and father both had blood type b. prisha and sebastian’s first child is a boy with type o blood. based on this information, sebastian’s blood type could be
multiple choice
either ab or o.
a only.
b only.
either b or o.
o only.

Explanation:

Step1: Determine child's genotype

Type O blood requires genotype $ii$. So the child inherited one $i$ allele from each parent.

Step2: Analyze Prisha's possible alleles

Prisha has type A blood, so her genotype is either $I^A I^A$ or $I^A i$. Since she passed an $i$ to the child, her genotype must be $I^A i$.

Step3: Analyze Sebastian's parent alleles

Sebastian's parents are both type B, so their genotypes are either $I^B I^B$ or $I^B i$. For Sebastian to pass an $i$ to the child, he must carry an $i$ allele. His possible genotypes from B parents are $I^B i$ (type B) or $ii$ (type O).

Step4: Confirm valid genotypes for Sebastian

Sebastian must pass an $i$ to the child, so his genotype can be $I^B i$ (type B) or $ii$ (type O).

Answer:

either B or O.