In the case below, were the babies switched? How do you know whether they were or they weren’t?

  • It was suspected that two babies had been exchanged in a hospital. Mr. and Mrs. Jones received baby #1 and Mr. and Mrs. Simon received baby #2  Blood typing tests on the parents and the babies showed the following:
  • Mr. Jones: Type A

    Mr. Simon: Type AB

    Mrs. Jones: Type O

    Mrs. Simons: Type O

    Baby #1: Type A

    Baby #2 Type O

     

     

    Expert Answers

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    The alleles for A and B are codominant and the allele for O is recessive. In order to produce an individual who is type O, each parent must contribute an O allele. The only parents who could possibly do that is the Jones couple. That is because Mrs. Jones who...

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    The alleles for A and B are codominant and the allele for O is recessive. In order to produce an individual who is type O, each parent must contribute an O allele. The only parents who could possibly do that is the Jones couple. That is because Mrs. Jones who is type O would supply one O allele and Mr. Jones, who is type A had to be heterozygous for type A meaning he has one A and one O allele in his genotype. He supplied the second O allele and the offspring was type O. The Simons couple could not be the parents of baby #2 since Mr. Simon can only contribute an A or B allele since he is type AB and could never produce an offspring with type O.

    Therefore, the babies were accidentally switched at birth.

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