New search
download case
  • Overview
  • Teaching Notes
  • Answer Key
  • Comments/Replies

Thomas and Sally

The Interplay of Scientific and Historical Evidence

Co Authors:

Eric Ribbens
Department of Biological Sciences
Western Illinois University

Andrew C. Lydeard
Department of Biological Sciences
Western Illinois University


Did Thomas Jefferson, third president of the United States, have children with his slave Sally Hemings? This PowerPoint clicker case explores this controversial question as students consider the evidence for Jefferson as the father of Eston Hemings, as well as the limitations of that evidence. In the process, students learn about Y-chromosomal and mitochondrial DNA and how they are passed down through generations. They also learn about the role of genetic tests in examining family lineages. In addition, the case serves to illustrate how science cannot always provide a direct and definitive answer and how conclusions often must be based on a mixture of scientific and historical (or other) evidence. The case was designed for an introductory biology course for non-majors but could easily be adapted for a majors' course or for the introductory portion of a genetics course. Students should have some prior knowledge of chromosomes and hereditability.

  • Understand the concept that Y chromosomal DNA can only be passed between male lineages.
  • Explain that mitochondrial DNA is passed solely from mother to offspring.
  • Explain the role of genetic tests when examining family lineages.
  • Analyze and interpret family pedigrees.
  • Explore the concept of scientific evidence within a larger social context that includes attitudes and other forms of evidence.
Keywords: Chromosomal genetics; inheritance; mitochondrial DNA; Y chromosome; short tandem repeats; STRs; family pedigree; forensics; Thomas Jefferson; Sally Hemings
Topical Area: Ethics, History of science, Scientific method, Scientific argumentation, Social issues
Educational Level: High school, Undergraduate lower division
Formats: PDF, PowerPoint
Type/Method: Clicker, Dilemma/Decision, Interrupted
Language: English
Subject Headings: Genetics / Heredity   Forensic Science   Biology (General)  
Date Posted: 12/5/2013
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

Case teaching notes are password-protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, begin the process by registering here.

Teaching notes are intended to help teachers select and adopt a case. They typically include a summary of the case, teaching objectives, information about the intended audience, details about how the case may be taught, and a list of references and resources.

  Download Teaching Notes

Answer Key

Answer keys for the cases in our collection are password-protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, begin the process by registering here.

  Get Answer Key
I can't wait to use this next semester in my Human Reproductive Biology course. This study is both compelling and informative. Thank you for your succinct, polished and interesting product.

Ann Hefner-Gravink
Solano Community College

City State:
security code
Enter Security Code: