Question

If a child has blood type O, and its mother has type A, could a man with type B be the father? why can’t a blood test be used to prove that he is the father?

Answer 1

Answer: Unfortunately, you cannot determine paternity by using the blood type method alone. Each person inherits ABO Blood Type from their parents.

Explanation: A man with type O blood would not be able to produce a child with type AB blood regardless of the mothers blood type. This is because type O blood is recessive and these individuals have two O alleles so the only allele they would be able to pass to a child would be "O".