Human Genetics Problem Set

Problem 10: Predicting inheritance pattern from pedigree analysis


A man who had purple ears came to the attention of a human geneticist. The human geneticist did a pedigree analysis and made the following observations:
In this family, purple ears proved to be an inherited trait due to a single genetic locus. The man's mother and one sister also had purple ears, but his father, his brother, and two other sisters had normal ears. The man and his normal-eared wife had seven children, including four boys and three girls. Two girls and two boys had purple ears. The purple-ear trait is most probably:
A. autosomal, dominant
A genetic trait that is passed from generation to generation to generation, from both fathers to daughters and mothers to daughters, is typically autosomal dominant.
B. autosomal, recessive
C. sex-linked, dominant
D. sex-linked, recessive
E. cannot be determined from this information

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Revised: November 5, 1998
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