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Cracking the Code of Life

Classroom Activities

Mystery Message

To help students understand the process involved in sequencing the human genome.

Materials for each team
  • two sets of the "Mystery Message" student handout, cut in different locations (PDF or HTML)
  • scissors
  • clear tape
Materials for teacher
  • slide of cheek cells stained with methylene blue
Procedure Tape strips illustration
  1. Before class, copy two sets of the Mystery Message student handout for each group. To prepare the sets for the activity, first cut out each column of letters. Next, attach them so that the symbol at the bottom of one column matches up with the symbol in the adjacent column. Once the symbols are matched up, cut out the symbols and use clear tape to join the two pieces together so that there is no space in between the letters. Continue this until you have one long sequence.

  2. Using a pair of scissors, cut the sequence of letters at four or five random locations. Do the same with the second sequence of letters, but make sure to cut the second sequence at different locations than the first. (You may want to laminate the cut pieces so you can use them again.)

  3. Carefully fold and place the two sets of fragments of the message in a plastic bag. Organize students into groups and give one bag to each group.

  4. Tell students that to sequence the genome, scientists decided to cut up into small pieces all the chromosomes that make it up. These pieces, then, could be sent to different research teams to be sequenced, or decoded. These decoded pieces are represented in the cut-up series of letters in each group's bag.

  5. Now comes the challenge: The genome needs to be put back together so that scientists can read the entire sequence. In each group's bag are all the pieces for one chromosome, but the group needs to figure out the original order.

  6. Have students work to find a technique that will allow them to reconstruct the correct sequence of one chromosome. What was the content of the message? What else, if anything, did students note about the message?

Activity Answer

In mapping the DNA sequence on a chromosome, scientists have found it faster to divide and conquer. The 24 chromosomes in the human genome (22 autosomes and the X and Y) are cut into many smaller fragments. Each fragment is sent to a different research lab to be sequenced. When the sequencing of these smaller fragments is completed, a computer is used to find the overlapping regions and put them into the correct order as found on the intact chromosome.

By overlapping sequences of letters, students should be able to arrive at the secret message coded on the original strip. The final message reads: "In order to speed up the sequencing of the human genome scientists had to break each chromosome into pieces and then overlap the pieces just as you have done in this aktivity"

Some students may notice that the final word in the sentence, aktivity, is misspelled. Explain to students that this represents a base-pair, or one-letter, mutation in the chromosome. Even a single base-pair mutation can cause a genetic illness.

Links and Books


Baker, Catherine. Your Genes, Your Choices: Exploring the Issues Raised by Genetic Research. Washington, D.C.: AAAS, 1999.
Describes the Human Genome Project, the science behind it, and the ethical, legal, and social issues raised by the project.

Marshall, Elizabeth L. The Human Genome Project : Cracking the Code Within Us. Minneapolis, MN: Econo-Clad Books, 1999.
Explores the process and technology used in sequencing a portion of the human genome. A chance to see the process of science through the eyes of the scientist. The author connects the discoveries in the human genome with the ethical implications they pose for society.

Reilly, Philip R. Abraham Lincoln's DNA and Other Adventures in Genetics. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press, August 2000.
Offers wide-ranging tales of crime, history, illness, and ethics to illustrate principles and issues of human genetics.

Sayre, Anne. Rosalind Franklin and DNA. New York, NY: W. W. Norton & Company, Inc., July 2000.
Offers a true life account of Franklin's work in elucidating the structure of DNA and explores the difficulties often faced by women in science. Franklin's research was central to the Nobel Prize-winning discovery of DNA, and Watson and Crick's discovery relied heavily on her pivotal X-ray crystallography data.

Watson, James D. The Double Helix: A Personal Account of the Discovery of the Structure of DNA. New York, NY: Simon & Schuster, 1998.
Chronicles the original story behind the race to discover the structure of DNA as seen through the eyes of James Watson.


Crick, Francis, and James Watson. "A Structure of Deoxyribonucleic Acid." Nature. Volume 171. 1953, Pages 737-738.
The seminal paper on the discovery of the structure of DNA.

"Outlook 2000: Inventing the Future." U.S. News & World Report, January 3, 2000.
Special double issue includes different articles about the Human Genome Project, which explain how the secrets of DNA may help cure illnesses and arrest aging, as well as outline the benefits and perils of genetic testing.

Web Sites

NOVA Online—Cracking the Code of Life
Provides program-related articles, interviews, interactive activities, resources, and more.

Genes and Disease
Shows what diseases have been mapped on which chromosomes. The Map Viewer presents a graphical view of the available human genome sequence data as well as cytogenetics, genetic, physical, and radiation hybrid maps.

The Human Genome Project
Provides background information on the Human Genome Project from the National Human Genome Research Institute. Several links provide more detailed resources describing the history and goals of the Human Genome Project.

Genetics Resources
Offers list of links with descriptions to more specific subject areas in the topic of genetics and medicine.


The "See Your DNA" and "Mystery Message" activities and the "Case Studies" activities align with the following National Science Education Standards:

Science Activities: Grades 5-8

Life Science

Science Standard C:
Life Science

Reproduction and Heredity

Molecular Basis of Heredity

Case Studies: Grades 5-8

Science in Personal and Social Perspectives

Science Standard F:
Science in Personal and Social Perspectives

Science and Technology in Society

Case Studies: Grades 9-12

Science in Personal and Social Perspectives

Science Standard F:
Science in Personal and Social Perspectives

Science and Technology in Society

Teacher's Guide
Cracking the Code of Life

Video is not required for this activity