Putting the Pieces Together

By Kevin M. Bonney

Abstract

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.

Download Case

Date Posted

07/28/2015

Overview

Objectives

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.

Keywords

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

Subject Headings

Biology (General)

Genetics / Heredity

EDUCATIONAL LEVEL

High school, Undergraduate lower division

FORMAT

PDF

TOPICAL AREAS

Ethics, History of science, Women in science

LANGUAGE

English

TYPE/METHODS

N/A, Debate, Demonstration, Discussion, Flipped

Teaching Notes & Answer Key

Teaching Notes

Case teaching notes are protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, purchase a subscription 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 Notes

Answer Key

Answer Keys are protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, purchase a subscription here.

Download Answer Key

Materials & Media

Supplemental Materials

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

Pule Chase Primer

Videos

The Chemical Structure of DNA
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
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
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
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
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.