A woman with blood type O has a child with blood type O. She claims that a man named Ralph is the child's father. Her claim would be proven false if Ralph has blood type: Check all that apply.

Question

_____  O
_____  A
_____  B
_____  AB

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain?

Gather Content
· What do you already know about single gene crosses and recessive and co-dominant alleles?

Consider Possibilities

· What other information is related to the question? Which information is most useful?

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

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?

Answer 1

_____  O
_____  A
_____  B
__X__  AB

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses a single gene cross with recessive and co-dominant alleles for blood type.
· What type of thinking is required?
        o You need to Analyze the information given to determine which blood type(s) are incompatible with Ralph being the father.
· What key words does the question contain?
        o Blood type O, A, B, and AB are phenotypes. They are determined by the alleles IA, IB, and i.

Gather Content
· What do you already know about single gene crosses and recessive and co-dominant alleles?
        o This question asks which paternal genotypes are incompatible with a child of blood type O, when the mother’s blood type is also O.
        o You know that blood type O is determined by the genotype i i – that is, two recessive alleles.
        o So both the mother’s genotype and the child’s must be i i.
        o What are the genotypes for each of Ralph’s possible blood types? Blood type A may be IA IA or IA i. Blood type B may be IB IB or IB i. Blood type O must be i i. Blood type AB must be IA IB.

Consider Possibilities

· What other information is related to the question? Which information is most useful?
        o Test out each possible cross in turn.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Since the child has two recessive alleles, we know that his father must have contributed a recessive allele.
        o Does that mean the father must be blood type O? (no)
        o If the father is blood type A, he could be IA i and contributed the i allele.
        o If the father is blood type B, he could be IB i and contributed the i allele.
        o If the father is blood type O, he is i i and contributed an i allele.
        o BUT, if the father is blood type AB, he can only be IA IB . There is no i allele to contribute.

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 remember that IA and IB are codominant alleles, but that the i allele is recessive?
        o Did you write out the crosses or use a Punnett square to help answer the question?
        o Did you realize that blood type A could be determined by a heterozygous IA i genotype?
        o Something to think about: is the mother’s blood type important for answering the question? Would the answer change if she was blood type B?