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Identifying Viruses

Identifying Viruses - by Viki Babcock
Illustration of a virus (middle/high school science)
Students learn the story of the 1918 influenza pandemic and about the use of electrophoresis and DNA fingerprinting to identify an unknown, using UPC barcodes to represent the DNA banding patterns.
Estimated class time

two 90-minute blocks

Lesson Objectives

Students will:
  • Learn about the history of the 1918 influenza pandemic.

  • Describe a virus and how it infects its host.

  • Simulate the creation of a DNA fingerprint via a Flash animation.

  • Analyze 'bar-code' DNA fingerprints to identify a virus.
Materials needed

  • Internet access

  • Copies of the video questions handout

  • Teacher-prepared sets of "DNA fingerprints" using UPC barcodes from assorted products. (See Preparation under Teaching Strategy.)

  • Video clips are available on the SECRETS OF THE DEAD: Killer Flu website, but if you wish to purchase the complete program, visit PBS Shop for Teachers http://shop.pbs.org/teachers/products/SEDE742
Teaching Strategy

Photo of a man infected by the Killer Flu

Teachers!
Video clips for your students are available here.

Video Clips
Preparation: Make DNA Fingerprint cards. Collect barcodes from a variety of products and cut them out, being sure to cut off the numbers if there are any present. You will need multiple copies of three different barcodes. Assign one product to represent the A-sample (bird virus), one for the B-sample (pig virus) and one for the C-sample (monkey virus), and label enough so that each group will have one of each. A complete set of codes should consist of one labeled Sample A, one labeled Sample B, one labeled Sample C, and 5 to 10 other codes, representing the unknown viruses. Include in each set of unknowns, some codes that match one or more of the samples A, B, or C. Identify the unknowns with a number or letter written on the back of the card. Glue the cut-out codes to index cards for ease of handling. To distinguish between complete sets of codes mount each set on a different color of index card or construction paper. Laminate for future use.

  1. Introduce the topic by starting a discussion about the flu. Ask the students if they've ever had the flu or if they know anyone who's had it. Then ask what causes the flu. What do they know about different types of flu? What is an epidemic? What is a pandemic?

  2. Show the video, SECRETS OF THE DEAD: "Killer Flu." In addition, or if preferred, direct students to the SECRETS OF THE DEAD Web site and have students explore the "Killer Flu" case file at http://www.pbs.org/wnet/secrets/
    case_killerflu/index.html    . Have students answer the video questions on the handout. Perhaps you will want to pause the tape and discuss the questions as each is addressed in the video.

  3. If the video is not available, instruct students to read the Background and Clues and Evidence pages at http://www.pbs.org/wnet/secrets/case_killerflu/index.html. Have students view the video clips on the Web site and write responses to the questions.


  4. Interactive
    Caught the Flu?

    After completing the interactive for this episode students should answer these questions.
    Have students explore the Interactive activity from the SECRETS OF THE DEAD site at http://www.pbs.org/wnet/secrets/
    case_killerflu/index.html    . Discuss as a class, or have students respond in writing to the accompanying questions.

  5. Discuss what a virus is and how a virus works. Direct students to How Viruses Work at http://science.howstuffworks.com/virus-human.htm for more general information on viruses and AMERICAN EXPERIENCE: "Influenza 1918" at http://www.pbs.org/wgbh/amex/influenza/index.html for information more specific to the 1918 virus.

  6. Explain to students it was important to completely identify the virus that was responsible for the 1918 pandemic and that the way to do that was through its DNA sequences. When scientists are comparing DNA samples, they are not looking at actual molecules of DNA, but at "DNA fingerprints" created through a process called electrophoresis. Direct students to Create a DNA Fingerprint at www.pbs.org/wgbh/nova/sheppard/analyze.html and allow students to work through the Flash animations, creating a DNA fingerprint.

  7. Divide the class into groups of two to three students each and provide each group with a set of UPC cards to represent the DNA fingerprints of mystery viruses. Explain that they have been hired by the CDC to determine which, if any, of the sample viruses have come from the known bird virus (A), the known pig virus (B), or the known monkey virus (C). Have students compare the unknown virus cards to each of the known samples to determine similarities. Groups can then switch card sets, if desired, for more practice. Students can be asked to display what they determine in a data table (which unknowns match which samples) and then to write a summary of what they've learned about viruses and using DNA to identify them.
Assessments

  • Written responses to video questions or participation in discussion.

  • Participation in online activities.

  • Data tables and summaries of activity.


Extensions

  • Refer to question 14 from the video questions handout. Have students research the ethics of using animals in virus research. Stage a debate presenting both sides of the issue.

  • Use outline maps to illustrate the spread of both the 1918 flu virus and the 2003 SARS outbreak. Research and compare the reactions of the medical community to each event.

  • Choose a particular virus, and research its history, its spread, and its mutations.

Correlation to National Science Standards

Standards from http://bob.nap.edu/html/nses/html/6e.html#csc912

CONTENT STANDARD C: As a result of their activities in grades 9-12, all students should develop understanding of the cell.

  • Cells store and use information to guide their functions. The genetic information stored in DNA is used to direct the synthesis of the thousands of proteins that each cell requires.
CONTENT STANDARD C: As a result of their activities in grades 9-12, all students should develop understanding of the molecular basis of heredity.
  • In all organisms, the instructions for specifying the characteristics of the organism are carried in DNA, a large polymer formed from subunits of four kinds (A, G, C, and T).

  • Changes in DNA (mutations) occur spontaneously at low rates. Some of these changes make no difference to the organism, whereas others can change cells and organisms.
CONTENT STANDARD E: As a result of activities in grades 9-12, all students should develop understandings about science and technology.
  • Science often advances with the introduction of new technologies. Solving technological problems often results in new scientific knowledge. New technologies often extend the current levels of scientific understanding and introduce new areas of research.


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SECRETS OF THE DEAD is a production of Thirteen/WNET New York. © 2006 Educational Broadcasting Corporation. All rights reserved.