In a particular human family, John and his motherboth have brachydactyly (a rare autosomal dominant allele causing short fingers). John’s father hasHuntington disease (another rare autosomal dominant allele). John’s wife is phenotypically normaland is pregnant. Two-thirds of people who inheritthe Huntington (HD) allele show symptoms by age50, and John is 50 and has no symptoms.Brachydactyly is 90% penetrant.a. What are the genotypes of John’s parents?b. What are the possible genotypes for John? Howlikely is John to have each of these genotypes?c. What is the probability the child will express bothbrachydactyly and Huntington disease by age 50 ifthe two genes are unlinked?d. How will your answer to part (c) change if insteadthese two loci are 20 m.u. apart?

In a particular human family, John and his motherboth have brachydactyly (a rare autosomal dominant allele causing short fingers). John’s father hasHuntington disease (another rare autosomal dominant allele). John’s wife is phenotypically normaland is pregnant. Two-thirds of people who inheritthe Huntington (HD) allele show symptoms by age50, and John is 50 and has no symptoms.Brachydactyly is 90% penetrant.a. What are the genotypes of John’s parents?b. What are the possible genotypes for John? Howlikely is John to have each of these genotypes?c. What is the probability the child will express bothbrachydactyly and Huntington disease by age 50 ifthe two genes are unlinked?d. How will your answer to part (c) change if insteadthese two loci are 20 m.u. apart?

Human Biology (MindTap Course List)

11th Edition

ISBN:9781305112100

Author:Cecie Starr, Beverly McMillan

Publisher:Cecie Starr, Beverly McMillan

Chapter19: Introduction To Genetics

Section: Chapter Questions

Problem 9CT

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