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Killer's Trail, The

Ideas from Teachers


(Gr. 9-12)
I developed three lessons based on two PBS Web sites. First, my students studied the relationship between DNA and proteins with the "A Science Odyssey" Web site's "DNA Workshop" interactive.

Then I had them visit NOVA "The Killer's Trail" Web site. This site allowed them to apply their understanding of DNA in solving a crime while learning about gel electrophoresis techniques.

Using the computer and NOVA resources provided my students with a unique way to learn about molecular genetics. Each student could progress at his own pace as he acquired knowledge. As a checkup, I gave the students mini-quizzes to evaluate their understanding. Bottom line: My students were enthusiastic about learning, and their quiz and test grades were better than students in the past who studied these topics using more traditional methods.

I have attached my lesson plan so that you can share it with your students.

Learn About DNA Using the Internet

Go to "A Science Odyssey" Web site's "DNA Workshop" interactive. Read the introduction and answer Questions 1 and 2 below.

  1. In which year were nucleic acids discovered?

    1. 1869
    2. 1940
    3. 1952
  2. Name the scientists who proposed an accurate model of DNA in 1952:

Click on the "DNA Workshop Activity" title. When the screen finishes loading, click on "DNA Replication" and answer the following questions.

  1. Where in the cell does DNA replication occur?

    1. cytoplasm
    2. nucleolus
    3. nucleus
    4. ribosomes

Follow the directions on the screen and answer the following questions.

  1. DNA is held into tight spools by:

    1. carbohydrates
    2. proteins
    3. nucleotides

  2. Describe the role of enzymes in the "unzipping" procedure.

  3. List the complementary base pairs that match up to create the rungs of the DNA ladder.

Return to the first screen and scroll to down the page to where you can learn more about DNA Replication. Select that choice and answer the following questions.

  1. The letters "D - N - A" stand for:

  2. The five elements found in every DNA molecule are:

  3. Label the model of DNA, using the following terms:

    5-carbon sugar (deoxyribose)
    nitrogenous base pair
    phosphate
  4. Circle a "nucleotide" on the model.

  5. Describe the steps of DNA replication in your own words by listing the three major steps.

    Step 1:

    Step 2:

    Step 3:

  6. How error-free is DNA replication?

When you have completed this and checked over your answers carefully (use your text, too), please hand this in to your teacher. Then pick up the worksheet on Protein Synthesis.



Learn About Protein Synthesis Using the Internet

Go to the "A Science Odyssey" Web site's "DNA Workshop" interactive and click on "DNA Workshop." When the screen finishes loading, click on "Protein Synthesis" and answer the following questions.

  1. Look at the cell model. Where is the DNA found that unzips when a protein is to be made?

    1. cytoplasm
    2. nucleolus
    3. nucleus
    4. ribosomes

Follow the directions on the screen and answer the following questions.

  1. When a protein is to be made, the DNA:

    1. found in all 46 chromosomes unzips.

    2. in all cells unzips.

    3. segment that is responsible for that particular protein unzips.


  2. List the RNA bases that pair up with the DNA nucleotides on the unzipped molecule during Transcription.

    DNA base      RNA base
    A
    T

    DNA base      RNA base
    C
    G
  3. How many nucleotides might be in a "real" mRNA molecule?

  4. The "m" in mRNA stands for:

  5. Once constructed, the mRNA leaves the cell's nucleus and travels to the:

    1. cytoplasm
    2. nucleolus
    3. nucleus
    4. ribosomes

  6. Find the single strand of mRNA attached to the ribosome. The mRNA bases are grouped into sets of three, which are called:

    1. amino acids
    2. anticodons
    3. codons
    4. genes

  7. tRNA molecules contain three exposed bases which are complementary to the codons of mRNA. These three bases on tRNA are called:

    1. amino acids
    2. anticodons
    3. codons
    4. genes

  8. The building blocks of a protein are attached to tRNA a molecules. These are specific:

    1. amino acids
    2. anticodons
    3. codons
    4. genes

  9. Complete the table after you've matched the tRNA molecules onto the mRNA template.

    mRNA codon      AUG  GGC  UCC
    tRNA
    amino
  10. Descibe what happens to the tRNA after it delivers its amino acid to the mRNA template.

  11. How many amino acids are found in a typical protein?

  12. Protein synthesis is completed when

    1. a special stop codon is reached

    2. the cell has no more amino acids available

    3. the ribosomes disintergrate

    4. the tRNA anticodons no longer match the mRNA codons

Return to the first screen and scroll to down the page to where you can learn more about Protein Synthesis. Select that choice and answer the following questions.

  1. As a result of its job in controlling protein synthesis, how is DNA able to direct all of the cell's activities?

  2. How many DNA nucleotides are needed to code out protein that contains 400 amino acids? Show your calculation here:

  3. How long will it take the cell to construct that protein?



Solve a Crime Using DNA
Go to the NOVA's "The Killer's Trail" Web site to read about a crime and be involved in finding the perpetrator.

  1. Who is the victim of the crime described in "It takes A Lickin'..."?

  2. What crime was committed?

  3. What substance is available at the crime scene from which a DNA fingerprint can be made?

Continue with Part 2:
Go to the "Create a DNA Fingerprint" interactive. Follow the directions to create a DNA fingerprint. Answer the following questions as you proceed.

  1. Why are restriction enzymes compared to "scissors"?

  2. Why will the DNA fragments be different lengths in different people?

  3. What is the purpose of the agarose gel that's poured into the electrolysis tray?

  4. Describe how the electrophoresis process separates the DNA fragments.

  5. Why are radioactive probes added to the separated DNA fragments?

  6. Which of Jimmy's sisters committed the crime?

Sent in by
Marcia Frye
Cortland Junior Senior High School
Cortland, NY


Teacher's Guide
Killer's Trail, The
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