DNA—a Molecular Identity

Grade level: 10–12

Description: In Lesson 1, students learn about what DNA is and several different DNA typing techniques. In Lesson 2, students examine three different situations where DNA typing was used to carry out justice. Students also identify and evaluate different uses of DNA typing techniques and its possible benefits and misuses.

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National science education standards

Science as Inquiry

• scientists rely on technology to enhance the gathering and manipulation of data. New techniques and tools provide new evidence to guide inquiry and new methods for gathering data thereby contributing to the advance of science.

Life Science

• cells have particular structures that underlie their functions.
• DNA, the molecular basis of heredity.

Science and technology

• science often advances with the introduction of new technologies.

Science in Personal and Social Perspectives

• progress in science and technology can be affected by social issues and challenges.

History and Nature of Science

• individuals and teams have contributed and will continue to contribute to the scientific enterprise.
• scientists have ethical traditions.
• science is not separate from society but rather science is a part of society.

Learning outcomes

The student will be able to:

• define what DNA is and describe its function in general terms.
• compare two different DNA typing techniques.
• describe different uses of DNA typing.
• identify possible benefits and misuses of DNA typing.

Time needed

Two 40-45 minute class periods

[Teacher's Note: One or a portion of the lessons can be conducted with computers (e.g., in a media center) where students can explore pre-selected Web sites.]

Materials

• an overhead projector and transparencies
• transparencies of DNA (312KB, PDF), Electrophoresis (190KB, PDF), and DNA Case Worksheet (54KB, PDF).
• copies of DNA, VNTR analysis, STR analysis, PCR analysis, RFLP analysis, and mtDNA analysis
• computers with the Internet connections to the following web sites; or printouts to be distributed among students:
  • Pitchfork Murder Case
  • Michael Blassie
  • Kirk Bloodsworth
  • DNA Timeline

Vocabulary

Allele:

any variants of a gene that may occur at a given location of a chromosome.

DNA:

deoxyribonucleic acid that is the molecular basis of heredity.

Electrophoresis (190KB, PDF)

 

Gene:

a hereditary unit which is a sequence of DNA located in a specific area of a chromosome that determines a particular characteristic in an organism.

Mitochondrion:

round or long cellular part that is found outside the nucleus, which produces energy for the cell through cellular respiration, and is rich in fats, proteins, and enzymes.

mtDNA:

DNA found in mitochondria outside of the nucleus.

Nucleotide:

compounds consisting of a nucleoside combined with a phosphate group that are the basic structural units of DNA and RNA.

Polymerase Chain Reaction (PCR) (1.1MB, PDF)

 

Restriction Fragment Length Polymorphism (RFLP) (563KB, PDF)

 

Short Tandem Repeats (STR) (177KB, PDF)

 

Single Nucleotide Polymorphism (SNP) (189KB, PDF)

 

Variable Number Tandem Repeats (VNTR) (141KB, PDF)

 

Procedures

Lesson 1

1. Assess students' assumptions and prior knowledge about DNA. What is DNA? What is its function? Where can you find it?
2. Review what DNA is in a classroom using a DNA (312KB, PDF) transparency.
3. Read aloud to students How does DNA help solve crimes?
4. Have students talk about the cases or situations that they know of where a DNA analysis has been used. Record students' contributions on a flip chart.
5. Review the recorded notes and, if appropriate, comment the diverse use of the DNA analysis—medicine, forensics, disaster, research, etc.
6. Explain to students that they will learn about different DNA analysis techniques.
7. Use the What is electrophoresis (190KB, PDF) transparency to introduce/review electrophoresis used in DNA analysis.
8. Have students work in teams of two and provide each team one of the following handouts:
   1. VNTR analysis (141KB, PDF)
   2. RFLP analysis (563KB, PDF)
   3. SNP analysis (189KB, PDF)
   4. STR analysis (177KB, PDF)
   5. PCR analysis (1.1MB, PDF)
   6. mtDNA analysis (342KB, PDF)
9. Explain that each team is to review the handout, research the given DNA analysis technique on the Internet, and prepare to present their findings to the class in 10–15 minutes.
10. Review each analysis technique by asking teams to share their findings. Meanwhile, ask students to evaluate whether one analysis may work better than another in a specific situation—e.g., old skeletal remains may have only enough DNA for mtDNA analysis.
11. Summarize the lesson by stating that the scientific work is often applied to solve societal challenges—one example being how DNA analysis may be used in identifying disaster victims. (if appropriate, refer to the list made from Lesson 1 Step 4.)

Lesson 2

1. Prepare students to explore three cases where DNA analysis was used in carrying out justice.
2. Distribute DNA Case Worksheet (54KB, PDF) to students and review question 1 of the worksheet. Have students work in teams of two and assign each team one of the following three cases. Ask teams to spend about 10 minutes to complete question 1 for their respective cases:
   1. Pitchfork Murder Case—this is the first case that used DNA tandem repeat testing to solve a double murder in England.
   2. Michael Blassie—this is the unknown soldier from the Vietnam War whose remains were identified and returned to his family after DNA testing became available.
   3. Kirk Bloodsworth—this is a case where a death-row inmate was exonerated through the DNA testing
3. Have teams share their findings while completing the case summary table using a transparency of the worksheet on an overhead projector.
4. Remind students that they discussed in Lesson 1 how DNA analysis can be used in many different situations. Review the notes taken from the discussion in Lesson 1 Step 4.
5. Review questions 2–4 of the worksheet and conduct a classroom discussion. First, allow students to write their own answers to these questions, then ask students to share their answers. [Teacher's Note: If appropriate, take a vote on "for" and "against", then ask students share their reasoning behind their votes.]
6. Ask students whether DNA typing should be available to everyone in the United States. Encourage students to explain why or why not.
7. Have students reflect on the three cases they examined earlier and the recent discussions. Ask students to answer question 5 of the worksheet and turn in the completed worksheet before the end of the class.

Evaluation

The group presentations, class discussions and completed worksheets serve as evaluation tools. Students demonstrate basic understanding of DNA and can describe at least two different DNA analysis techniques. Students can identify different situations where DNA analysis is used in modern society and consider its ethical uses.

Extension

• Research and write about any positive and/or negative consequences of establishing an international DNA database.

Contributors