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At your job as a genetic counselor, your client is a distraught young woman. She

ID: 81963 • Letter: A

Question

At your job as a genetic counselor, your client is a distraught young woman. She explains to you that her mother has blood type A, her father has blood type AB, and she has blood type O. She has been told that this is not genetically possible. Your initial suspicion in this case is that there was infidelity (i.e. her father is not really her father), but the young woman refuses to accept this explanation. For her sake, you agree to investigate other possibilities. Your assignment in this project therefore is to determine if there is a logical genetic explanation for this scenario, or if infidelity must be concluded. In formulating your answer, be sure to include explanations of how multiple alleles and epistasis affect inheritance patterns. At your job as a genetic counselor, your client is a distraught young woman. She explains to you that her mother has blood type A, her father has blood type AB, and she has blood type O. She has been told that this is not genetically possible. Your initial suspicion in this case is that there was infidelity (i.e. her father is not really her father), but the young woman refuses to accept this explanation. For her sake, you agree to investigate other possibilities. Your assignment in this project therefore is to determine if there is a logical genetic explanation for this scenario, or if infidelity must be concluded. In formulating your answer, be sure to include explanations of how multiple alleles and epistasis affect inheritance patterns. At your job as a genetic counselor, your client is a distraught young woman. She explains to you that her mother has blood type A, her father has blood type AB, and she has blood type O. She has been told that this is not genetically possible. Your initial suspicion in this case is that there was infidelity (i.e. her father is not really her father), but the young woman refuses to accept this explanation. For her sake, you agree to investigate other possibilities. Your assignment in this project therefore is to determine if there is a logical genetic explanation for this scenario, or if infidelity must be concluded. In formulating your answer, be sure to include explanations of how multiple alleles and epistasis affect inheritance patterns.

Explanation / Answer

We can prove that it is the case of infidelity.

Blood grouping is an example of multiple allele interaction in which blood groups are produced by combination of three different alleles i.e IA,IB and i alleles.IA,IB are dominant over i.

Blood type A means :IAIA or IA i

Blood type B means:IBIB or IBi

Blood type O means:ii

Blood type AB means :IAIB

For the women to have blood group O, she has to have genotype ii which means she has to inherit one i from mother (if mother is IA i) and one i from father which is not possible in this case as father has no i allele.

This is not a case of epistatic inheritance as in epistatis there occurs interaction of genes and not alleles as in case of multiple allele interaction.