In Sickness and in Health

A Trip to the Genetic Counselor

Author:	Barry Chess Natural Sciences Division Pasadena City College bxchess@pasadena.edu
Abstract:	In this interrupted case study, Greg and Olga, a young couple planning a family, have decided to see a genetic counselor because of a family history of genetic disease. Students construct a pedigree from the information presented in the case; then, on the basis of that, determine if the couple are carriers for any recessive genetic diseases and the likelihood of their passing those diseases on to their children. Students learn about the inheritance of single gene dominant, recessive, and sex-linked disorders as well as the significance of carrier frequency. Originally developed for use in a non-science major general biology course, the case has also been used in a human genetics course for non-science majors.
Objectives:	Construct a pedigree from a written narrative. Be able to determine, from a pedigree, carriers of recessive genetic diseases and the probability that they will pass those diseases on to their offspring. Understand the rules governing the inheritance of single gene dominant, recessive, and sex-linked disorders and be able to apply them to analyze simple genetics problems. Be able to determine the carrier frequency of a trait given the prevalence of the trait in the population, as well as understand the significance of carrier frequency.
Keywords:	Genetic counseling; chromosome; homozygous; heterozygous; allele; pedigree; autosomal inheritance; sex-linked inheritance; population genetics; myotonic dystrophy; Hardy-Weinberg; dominant; recessive; genetic disease
Topical Area:	Ethics
Educational Level:	High school, Undergraduate lower division
Formats:	PDF
Type/Method:	Interrupted
Language:	English
Subject Headings:	Biology (General) Genetics / Heredity
Date Posted:	04/26/06
Date Modified:	N/A
Copyright:	Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

Teaching Notes

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Answer Key

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I used this case at the end of a semester-long non-majors course on Heredity, Evolution, and Society. We spent about two hours on this case. Students were split into groups of four or five with each group having at least one strong student. I also let each group know that it was important for everybody in the group to understand the problems and answers since I could call on anybody to give the consensus answer.

My students loved this case study since it really helped to tie in concepts that we had gone over all semester and that they had trouble with. In particular, the idea of X-linked versus recessive, writing genotypes, and identifying carriers. This was a great way to have them construct pedigrees and go over the basic concepts of genetics in time for the final.

Thanks for writing this well-designed case.

Chaya Nanavati
Department of Biology
Ohlone College
Fremont, CA
cnanavati@ohlone.edu
5/15/2006

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