The Case of the Long Lost Son
The story you will read in the next paragraph is fictitious, but there are many examples in real life of stories similar to this one. Read the story and answer the questions that follow. See if you would have made the same decisions that the judge in the story made.
Mr. Cash died and left all his money to his two children. A young man claiming to be a lost third child sued for his share of the estate. The judge ordered blood tests for all family members and the young man. Mr. Cash’s blood type was already on record. He had type AB blood. His wife had type A, and the young man who claimed to be the long lost son had type O blood. The judge quickly dismissed the case.
INQUIRY: How can Punnett squares be used in genetic crosses of blood types?
PROCEDURE:
1. Use the following genotypes and phenotypes to describe the possiblegenotypes and phenotypes of Mr. and Mrs. Cash’s offspring.
Genotypes that would produce phenotype A: IAIA and IAi
Genotypes that would produce phenotype AB: IAIB
Genotypes that would produce phenotype O: ii
2. Using the Punnett square below, diagram the offspring that could be produced if Mrs. Cash had genotype IAIA and Mr. Cash had genotype IAIB. What could result from this mating? Include % genotypes and % phenotypes.
3. Using the Punnett Square below, diagram the possible offspring if Mrs. Cash had genotype IAi and Mr. Cash had genotype IAIB. List the % genotypes and % phenotypes that could result from this mating.
ANALYSIS AND CONCLUSION:
1. What are the possible genotypes of a person having blood type O?
2. What is the genotype of the young man claiming to be Mr. Cash’s long lost son?
3. Do you agree or disagree with the judge’s decision? Why?
4. Why did you have to do two Punnett squares to figure this case out?