Susan, a mother with Type B blood, has a child with Type B blood. She claims that Craig, who has Type O blood, is the father. He claims that he cannot possibly be the father. The judge aced her
BIO30 class, so she rules that:

a: susan cant be the real mother of the child; there must be an error at the hospital

b: susan is right and craig must pay child support

c: all of the above

d: its’s impossible to reach a decision based on the limited data available

A child with type B blood can have a mother with type B blood and a father with type O blood so the judge grants her request and decides due to Susan is right and Craig must pay child support (option b).

Explanation:

Susan is right in this case because her son with type B blood may have a mother with type B blood and a father with type O blood.

Blood types, according to the ABO system, depend on the existence of surface antigens A or B —Types A, B and AB— or their absence in the erythrocyte membrane.

In the inheritance of blood groups A and B are co-dominant, while the absence of antigens —type O— is a recessive trait.

Assuming that Susan has a genotype B/B and that Craig has a genotype O/O:

Alleles      O     O

B            B/O  B/O

B            B/O  B/O

So it is very likely that the child is Craig's son and Susan is right.