Activity: Guilty or Innocent?

Goals:

  1. To simulate how DNA profiling can be used to

provide evidence related to a crime.

  1. To draw conclusions about which suspect was present at the crime scene based on the comparison of the patterns of bands on bar codes.

Background Information:In courtrooms across the country, a genetic technique called DNA profiling or DNA fingerprinting is being used to help solve crimes. For years the fingerprints on the fingers of hands have been used to identify people, because no two people have the same fingerprints. Detectives routinely use fingerprints found at a crime scene to help identify the person who committed the crime. In a similar way, DNA from samples of hair, skin, and blood can also be used to identify a person. No two people, except for identical twins have the same DNA.

In DNAprofiling, enzymes are used to cut the DNA in the sample found at a crime scene into fragments. An electrical current then separates the fragments by size to form a pattern of bands. Each person’s pattern of bands is unique. The DNA pattern can then be compared to the pattern produced by DNA taken from people suspected of committing a crime. (This information is printed from Science Explorer: Cells & Heredity, page 131.)

Materials:a SUSPECT CARD with a variety of bar codes, a hand lens

Procedure:

  1. What I Know: Write two sentences about what you already know about DNA profiling.
  1. Read the following scenario:

  1. Examine the 21 suspects’ DNA patterns (Universal Product Code “UPC” labels on the SUSPECTCARD (handout).
  2. Cut out the DNA Evidence pattern (on the last page of this packet) along the dotted lines. It is the “DNA” fingerprint of the strands of hair found on the windowsill at the scene of the crime.
  3. Compare the DNA Evidence pattern with the 21 suspects’ DNA patterns found on the SUSPECT CARD to find a possible match.
  1. What I Observed: For this section write down the letter of the suspect that matches with the DNA evidence pattern. If available, glue the matching suspect DNA in the space provided.

Letter ______

DNA Evidence Pattern Matching Suspect DNA

  1. Questions: Answer the following questions in complete statements.
  2. Did the suspect commit the burglary? Explain your answer.
  1. When would DNA fingerprinting be used in a criminal investigation?
  1. Why is the term fingerprinting an appropriate name for this technique?
  1. Explain why Universal Product Code “UPC” labels are a great simulation for DNA patterns?
  1. Technology: To learn more go to:

to answer the following questions.

  1. If people are blood relatives, is their DNA similar?
  1. Is DNA evidence alone enough to acquit or convict?
  1. Can DNA evidence exonerate (free from a charge of guilt) wrongfully convicted prisoners?
  1. What I Wonder: Pose a question that you may have concerning DNA fingerprinting
  1. Claim and Evidence Writing Prompts: Use the following prompts to help you construct your lab conclusion, What I Learned.
  • Goal: State the goal of this lesson.

The goal of this lesson is…

  • Claim: What did you learn from the activity that satisfies the goal of this lesson? This is an I Learnedstatement.

I learned that…

  • Evidence: How can you prove from your observations that you learned what you claim? This can be a general statement that you will explain in detail in your explanation.

I know this because….

  • Explanation: Use specific data from your observations to support your claim and describe the evidence. Use details to support your claim.
  • Concluding Statement: Reword the goal and either add information you learned about the topic from your text book, class discussions, and/ or personal research OR you can extend the statement by adding a relevant question.
  1. What I Learned:Write at least a one paragraph summary of what you learned from completing this activity. Use the Claims and Evidence Writing Prompts to help you compose your summary.