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MERLOT II


    

Peer Review


The Genetic Code

 

Ratings

Overall Rating:

5 stars
Content Quality: 5 stars
Effectiveness: 5 stars
Ease of Use: 5 stars
Reviewed: Jan 24, 2007 by Biology Editorial Board
Overview:

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.

Learning Goals: 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
Recommended Uses: 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.
Technical Requirements: Current internet browser with Flash Player and QuickTime is needed to see animations and view video clips.

Evaluation and Observation

Content Quality

Rating: 5 stars
Strengths:
  • 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 DNA—how 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
  • Animations accurately represent experimental designs presented
  • Rich source of information on personalities, history, and current thought on these concepts
Concerns:
  • 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

Rating: 5 stars
Strengths:
  • 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.
Concerns:
  • 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

Rating: 5 stars
Strengths:
  • 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
Concerns:
  • None

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.