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BLOOD TYPE PRELAB WORKSHEET
1. Using the following genotypes for blood, predict the possible and impossible blood types
of children produced from these parents.
Possible
Impossible
a. A x A
A A
(AA x AA)
A
A
b. O x AB
(OO x AB)
c. AB x A
(AB x AA)
A
B
A
A
O
O
A
B
2. The Charlie Chaplin case. In 1941, Charlie Chaplin became romantically involved with a
young actress named Joan Barry. In 1943, twenty months after the relationship ended,
she had a child and claimed Charlie Chaplin as the father. A paternity suit ensued. Chaplin
had type O blood. Barry had type A blood. The baby had type B blood. Was the baby
Chaplin’s? (Yes, No) Provide written explanation and/or charts like those above to support
your answer.
3. A father with type B blood and a mother with type O blood have a baby with type O
blood. Which of the following is the father’s genotype: AA, AB, AO, BB, BO, OO
4. What is the only combination of parental blood types with the potential to produce a
child of with any of the following types of blood: type A(AA), B (BB), AB or O (OO)?
Which are the parental genotypes: AA, AB, AO, BB, BO, OO?
5. A type AB father and a type A (AA or AO) mother are having a baby. What is the
probability that the baby has type A blood? Type B? Type AB? Type O?
Answers to Blood Type Problems
1. a. possible: A, O
impossible: B, AB
b. possible: A, B
impossible: O, AB
c. possible: A, AB, A
impossible: O
2. a. The baby could not have been Chaplin’s, since the B allele carried from the baby did not
come from its mother and could not have come from Chaplin either. Three pathologists
testified to this effect. However, the jury was undeterred by the “scientific evidence” and ruled
that Chaplin was the father, ordering him to pay child support.
3. The father’s genotype must be Ibi (BO).
4. The parents’s genotypes must be Ibi (BO) and Iai (AO).
5. You don’t know if the mother is AO or AA. Therefore you have to do both Punnett’s squares
and add the probabilities. The probability of A: 4/8; AB 3/8; B 1/8; O 0/8. If you KNEW she had
the AA genotype, the probabilities would be A: 2/4; AB 1/4; B 0/4; O 0/4. If you knew she had
the AA genotype, the probabilities would be A: 2/4; AB 1/4; B 1/4; O 0/4.
The data is PROBABLY consistent with AO x AB. It is not consistent with AA x AB.