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Putting the Pieces Together: The Discovery of DNA Structure and Replication


Kevin M. Bonney
Liberal Studies, Faculty of Arts and Sciences
New York University


This case study provides an overview of the seminal experimental work that led to the discovery of DNA structure and the confirmation of the semi-conservative model of DNA replication. By guiding students through a chronological series of historic experiments and discussing some of the collaborations and controversies involved in the original research, students learn about the history and nature of science in addition to several important biological concepts. A number of recommended videos, including one created by the author, enable instructors to use the "flipped-classroom" mode of instruction according to which students read primary literature and watch videos on their own before group discussions and activities. The case study was developed for use in an introductory undergraduate biology course, and would also be appropriate for use in a high school biology course. Some prior knowledge or instruction may be required, depending on the level and learning objectives of the course.


  • Describe the structure of DNA.
  • Summarize the specific contributions of Watson and Crick, Franklin, Wilkins, and Meselson and Stahl to discovering the structure of DNA and how DNA is replicated.
  • Justify, argue, and evaluate the ethical implications of the controversy surrounding the role of Rosalind Franklin in the discovery of DNA structure.
  • Compare and contrast the conservative, dispersive, and semi-conservative models of DNA replication.
  • Identify the model of DNA replication supported by the Meselson and Stahl experiment.
  • Describe how Meselson and Stahl experimentally demonstrated how DNA is replicated.
  • Describe the connection between DNA structure and function.


DNA structure; DNA replication; double helix; deoxyribose nucleic acid; dispersive; conservative; semi-conservative; Photo 51; Watson and Crick; Rosalind Franklin; Meselson and Stahl

Topical Areas

Ethics, History of science, Women in science

Educational Level

High school, Undergraduate lower division



Type / Methods

N/A, Debate, Demonstration, Discussion, Flipped



Subject Headings

Biology (General)  |   Genetics / Heredity  |  

Date Posted


Teaching Notes

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Supplemental Materials

The supplemental material below can be used with this case study.

  Pule Chase Primer hhmi/

Answer Key

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The following video(s) are recommended for use in association with this case study.

  • The Chemical Structure of DNA hhmi/
    This video uses an animation to illustrate the structure and main properties of DNA. Running time: 2:44 min. Produced by Howard Hughes Medical Institute (HHMI).
  • The Secret of Life—Discovery of DNA Structure
    This video describes the contributions of several key scientists involved in the discovery of the structure of DNA. Running time: 8:36 min. Produced by Virginia Commonwealth University, 2014.
  • Building a Model of DNA Replication
    This video shows a demonstration of the conservative, dispersive, and semi-conservative models of DNA replication using marshmallows and gum drops. Running time: 3:19. Created by Kevin M. Bonney for the National Center for Case Study Teaching in Science, 2015.
  • The Double Helix hhmi/
    The Double Helix is the story of the scientists and evidence involved in one of the most important scientific quests of the 20th century: the discovery of the structure of DNA. Running time: 16:53 min. Produced by HHMI BioInteractive.
  • DNA Replication Schematic hhmi/
    A 50-second animation that explains the mechanism of replication. The double helix unwinds and each strand acts as a template for the construction of the new DNA molecule. Running time 0:50 min.Produced by HHMI BioInteractive.
  • DNA Replication Basic Detail hhmi/
    Short 3-D animation showing how DNA is replicated at the molecular level. It involves an enzyme that unwinds the DNA and other enzymes that copy the two resulting strands. Running time: 1:07 min. Produced by HHMI BioInteractive.second
  • DNA Replication Advanced Detail hhmi/
    Short animation showing both strands of the DNA double helix acting as templates for the new DNA strands. Incoming DNA is unraveled by the enzyme helicase, resulting in the 3' strand and the 5' strand. The 3' strands and the 5' strands are replicated by a DNA polymerase enzyme but in different ways. Running time: 2:20 min. Produced by HHMI BioInteractive.