Human Blood Type Sample Problems

Table 1: The following table gives information on human blood types needed in problems below. Alleles of types I_A and I_B are dominant over type i.

1. A patient is rushed to the emergency room and has suffered severe blood loss. Type AB blood is in short supply, but the nurse says "Don't worry, he's type AB positive. We can give him any kind of blood." Explain. (Why is type AB called the universal recipient?)

2. On the battlefield, a medic is treating a soldier who has lost a great deal of blood. They are out of blood typing supplies so the medic, who is Type O negative, simply donates his own blood to the patient. Why could this work? (Why is Type O called the universal donor?)

3. There is a practical joker in the maternity ward who removed all the baby id bracelets. There are three babies that cannot be easily distinguished and the parents want to be sure they get the right ones back so the doctors do a blood test. A particular mom is homozygous type A and the dad is type O. The babies have blood types AB, A, and O. Show your work below and indicate which baby must be theirs.

4. The police have rounded up the usual suspects in the latest rash of textbook thefts. The thief got a nasty paper cut at the scene of the crime. The suspects are of blood types O, A, B and AB. The blood at the crime scene contained i alleles. Which suspect therefore cannot have been involved? Explain.

Release Suspect # ____ because...

5. In a paternity case, a single mother claimed that a certain man was the father of her baby. The man denied it, claiming that her current boyfriend was the father. The court ordered a blood test (this was in the days before DNA testing). The mother was Type O and the baby was Type O. The man was Type AB. Is it possible that he was the father? Why or why not?

6. Why is it that a blood type test can only disprove but never prove paternity?

 7. (True Story) In Denmark, a husband and wife who had been unsuccessfully trying to have a baby went to a fertility clinic. Sperm and eggs were collected from father and mother, and combined in a petri dish, creating several "test-tube babies". These babies were implanted in the mother and 9 months later she delivered twins, one with light skin and one with dark skin. Because this seemed strange, a DNA test was conducted and it was found that both children were related to the mother, but only the light skinned child was related to the father. What must have happened?

8. Rh factors are proteins that were first discovered in the blood of Rhesus Monkeys, but humans have them too. If you are Rh positive, it means that there are Rh type proteins in your blood. If you are Rh negative, there are no Rh type proteins in your blood. Problems can arise when an Rh negative mother has a child who is Rh positive. Why does the mother's body attack her own baby in this situation?