Three babies were recently mixed up in a hospital. Based on the data in the table below, the couple with blood types A and B are the actual parents of the child with blood type
A. O
B. B
C. AB
D. none of these babies could be the child of the couple with blood types A and B
C. AB
Clarify Question
· What is the key concept addressed by the question?
o This question addresses blood type alleles.
· What type of thinking is required?
o You need to Analyze the information given to determine which baby goes with which parents.
· What key words does the question contain?
o Remember, the blood types A, B, AB, and O are the phenotypes. They result from genotype combinations of the alleles IA, IB, and i.
Gather Content
· What do you already know about blood type alleles?
o Blood type alleles can be recessive (i) or co-dominant (IA and IB).
o Some blood types are specified by a single genotype (e.g., blood type O is always i i), but some can be specified by two possible genotypes (blood type A could be IA IA or IA i).
Consider Possibilities
· What other information is related to the question? Which information is most useful?
o The A and B parents could each be homozygous or heterozygous with an i allele.
o They could have produced the blood type O baby by contributing their i alleles. They could have produced the B baby by contributing an i and a IB allele. Or they could have produced the AB baby by contributing the IA and IB alleles.
o We need to figure out the other combinations to answer the question!
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o Let’s consider each of the babies in turn:
o The baby of blood type O must have received two i alleles. What parents are possible? (A and B, A and A, or B and O)
o The baby of blood type B must have received alleles IB and i (since there aren’t two B parents). What parents are possible? (A and B, or B and O)
o The baby of blood type AB must have received alleles IA and IB. What parents are possible? (only A and B!) So we can assign the AB baby to parents A and B.
o We can now determine that the baby of blood type B must be from the B and O parents, and finally the only parents left for the O baby are the A and A parents, who must have each contributed an i allele.
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
o This question required you to Analyze the information given, using logic, to dissect the problem and determine the answer.
o Did you recognize that the A and B parents could in theory have produced any of the babies (by contributing one or more i alleles)?
o Did you use a pencil and paper to help work out this question?
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