This module on The Genetic Code is from the Supersite "DNA From the Beginning." Deciphering the genetic code is described in this learning object through the work of Marshall Nirenberg, Har Khorana, Heinrich Matthaei, Phil Leder, Robert Holley, and others. The parsimony principle (simplest solution is usually right) is introduced to show how scientists proposed sets of three nucleotides to form a codon. Virtual experiments are provided to show how these codons were deciphered and the importance if tRNA in translation of mRNA into protein. This unit is organized as a couple dozen concepts that delineate how scientists came to understand the fundamental ideas. This tutorial begins with a brief outline of the questions that lead to understanding the mechanisms involved. A more in-depth examination of the concepts is achieved through the animation menu, which accesses an animated tutorial of the basic experimental design(s) and critical thinking processes that led to the understanding of the principle. Users may access the "Problem" menu, which presents several multiple choice questions requiring interpretation of the experimental results presented in the tutorial. The questions are instantly graded, providing immediate feedback. The problem in this tutorial details how changes in the genetic code of the DNA (mutations) will impact the translation of that code. Additional menus are: the "Picture Gallery," with images of historical photographs of researchers, lab, and laboratory equipment used in the experiments described; the "Audio/Video" menu, that presents QuickTime interviews with researchers who discuss the concept in more detail; and a "Biography" menu, providing further information about the key scientists. A "Links" menu provides further bibliographic information, as well as links to additional relevant sites.
Describe the experiments and thought processes used by Nirenberg, Khorana, Matthaei, and Leder to break the genetic code. Also details impact of different types of mutations on this process.
Target Student Population:
Advanced high school as well as undergraduate and graduate students
Prerequisite Knowledge or Skills:
No prerequisite knowledge is required, but some background in chemistry, genetics, and molecular biology may help users better understand the information. Ability to use web browser with Flash and QuickTime will be required.
Type of Material:
Tutorial and Animation / Interactive Lesson
This material can be used in lecture or for independent study to learn about molecular genetics. It could also be part of an online learning course.
Current internet browser with Flash Player and QuickTime is needed to see animations and view video clips.
Evaluation and Observation
Very clear and accurate description of the experiments by Nirenberg, Khorana, Matthaei, and Leder that lead to an understanding of the genetic code
Content follows logical progression both conceptually and temporally
Very complete and accurate information with appropriate vocabulary
Emphasizes scientific approach to understanding through clear explanations of how the evidence was used to construct the model of DNAhow we know, not just what we know
The interactive problem in this unit presents a very clear and concise description of how different types of mutations will impact decoding of messenger RNA
Rich source of information on personalities, history, and current thought on these concepts
Perhaps the titles of the units could be modified to more closely delineate the topic(s) covered
The site needs more video interviews from other scientists in addition to the excellent clips of Marshall Nirenberg. These interviews are valuable tools for learning and understanding the methods of science
Some researchers mentioned in the tutorial do not have biographies
Potential Effectiveness as a Teaching Tool
Excellent source of tutorial information
Tutorials promote understanding of basic concepts and contain more than one approach to understanding the concept
Tutorial animations and problems lend themselves to the creation of additional questions such as "where do we go from here?"
Interactive quizzes provide immediate reasons for correct and incorrect answers
Biography, audio/video clips, and photo gallery provide a historical and personal background usually missing from educational materials; these help students understand the human side of science
The animations represent an excellent collection of scientific reasoning and logic, and focus on "how we know" not just "what we know." The animations frequently begin with a famous scientist posing a problem to be solved. This approach may make more of a connection between the results of a classical experiment and the mind behind the reasoning. The constant flow of scientific reasoning from unit to unit provides a clear and impressive thread of logic showing how scientists realized how the genetic code worked.
The tutorials could be improved by adding sound and expanding upon the interactivity of some of the Flash Player animations
Ease of Use for Both Students and Faculty
Clear and accurate instructions
Well designed, easy to navigate, intuitive and fast
Widespread and effective use of animation
Definitions linked directly to the term
Audio glossary gives detailed explanation of term as well as pronunciation
Organization of tutorial leads the user through the concept
Excellent use of Flash Player and QuickTime video clips
Other Issues and Comments:
The animations represent an excellent collection of scientific reasoning and logic, and focus on "how we know" not just "what we know." The animations frequently begin with a famous scientist posing a problem to be solved. This approach may make more of a connection between the results of a classical experiment and the mind behind the reasoning. The constant flow of scientific reasoning from unit to unit provides a clear and impressive thread of logic showing how scientists realized that DNA is the genetic material. It might help to add more video interviews from other scientists, especially where there is only one person featured in the video clips. Perhaps modern scientists could substitute for those who cannot be interviewed. A few female and minority scientists would be a plus for this part of the site. These interviews are valuable tools for learning and understanding the methods of science. The authors might consider adding sound and expand upon the interactivity of some of the Flash Player animations.