A Lab Trilogy for Beginning Biology Teachers

Sally Bishop
1994 Woodrow Wilson Biology Institute

To the teacher: So much of what we do is aimed at the "seasoned" teacher that I decided to do three simple laboratories for the beginning teacher: Building a DNA Molecule, Mitosis in Motion and Mutation Gossip. These labs require minimal equipment. They were written for ninth and tenth grade biology students.

Lab I - Building a Dna Molecule

Materials Needed:

Toothpicks

Cord - the kind you use to draw curtains

Compass

Elmer's glue

Colored markers or paint

Artist's paintbrush (if you use paint)

To the Teacher:

Review the structure of DNA. Do lab. At the END of this lab it is fun to notice the VARIATION in the number and sequence of base pairs. Students should be able to explain their models to other students and to their parents. Then students like to decorate the room by hanging the models or constructing mobiles of a number of models. As always, students like to be "stars" so you might want to take still pictures (or slides) or to videotape them working so they can see themselves constructing the model after they're done.

To Students:

Color or paint the cord using two different colors. Make the first segment of the cord long and paint it according to a key that you should make as you construct the molecule. Call that section deoxyribose sugar. Color or paint a short section below the long section using a different color and key it for phosphate. Alternate deoxyribose sugar and phosphate segments. Color or paint the second piece of cord to identically match the first.

MOLECULE	COLOR
Deoxyribose
Phosphate

Using the compass, poke holes in the center of each deoxyribose sugar segment on both cords. Be careful not to accidentally poke yourself!

Make a key for the four bases telling the name and color you've chosen for each. Also pick a color for your hydrogen bond:

BASE	COLOR
Adenine
Thymine
Guanine
Cytosine
Hydrogen bond

Divide each toothpick into two unequal parts (l long and l short) with a thin ring of color around the toothpick to represent a hydrogen bond. Then color or paint some of your toothpicks making sure the purine (adenine) is correctly paired with the pyrimidine (thymine). The purine part of the molecule should be LONGER than the pyrimidine part of the molecule and the two should be joined by the hydrogen bond.

Similarly, color or paint the other toothpicks making sure the purine (guanine) is correctly paired with the pyrimidine (cytosine). Again, the purine part of the molecule should be LONGER than the pyrimidine part of the molecule and the two should be joined by the hydrogen bond.

After the cords and toothpicks have dried, use Elmer's glue to hold the toothpick bases in the deoxyribose part of the cord. Dry. Twist and compress the molecule in a small jar so that it simulates the double helix shape of a DNA molecule.

SAMPLE PICTURE

Untwisted DNA Molecule

Lab II -"Mitosis in Motion" Flip Cards

To the Teacher:

Teach mitosis. Have students look at prepared slides of Allium root tip mitosis (or have them make their own plant meristem mitosis slides). After you're fairly certain the class has grasped the idea of mitosis, ask them to prepare a "Mitosis in Motion" flip card show. It's usually a good idea to have students draw this on paper first to be checked by the teacher or members of a cooperative learning group before graduating to the card show so the cards will be accurate. Also, the teacher may wish to do a demonstration using a simple concept like "A Rising Sun" to illustrate what a "Flip Card" show should look like.

Materials Needed:

3" x 5" index cards CUT IN HALF

Colored pencils, pens or markers

Staples

Stapler

To the Student:

Use halved 3" x 5" ndex cards to make a "Mitosis in Motion" flip card show. It should be about thirteen cards long. The first card must be a title card which might include things like theater name, title of the program, actors (number of chromosomes), rating, etc. Since you'll be stapling the cards on the left side, center your mitosis show in the right three-quarters of the card. Suggestion: Make the second card interphase showing chromatin; cards 3-5 should represent prophase; card 6 should be metaphase; cards 7-9 represent anaphase; cards l0-l2 are reserved for telophase and the last card should show two daughter cells.

When you get ready to put the show together (i.e. staple it), prepare the cards as though you were going to shuffle them by hitting the cards on the table to make the edges equal and then bend them slightly to stagger the edges for better flipping. Staple and show.

Acknowledgment:

This lab was graciously shared by Norman Rubel, Lakeview High School, Battle Creek, MI 490l5

Lab III: Mutation Gossip

This lab is a take-off on the old game of "Gossip."

Arrange the class into one long line. Give the first person in the line a LONG sentence. It can be a tongue twister or any other sentence you think might manage to be "garbled" as it moves its way up the DNA of a chromosome of people. Ask the first person to remember the sentence. Each person must say the sentence to their contiguous gene (neighbor) ONLY ONCE. If the neighbor gene doesn't hear it the first time, they must repeat what they think they heard. After everyone has said the sentence to their neighbor, ask the last person to repeat the sentence out loud. Compare it to the sentence the first person was given by you. Invariably, if you have a large class, the sentence is changed somewhere in its transmission. This represents a "mutation" analogous to the mistakes made when DNA replicates.

There are many variations on this lab such as having two lines to more closely simulate replication where one chromatid has the correct answer and the other plays "Mutation Gossip." The best might be to have each gene in a chromatid tell its corresponding gene in the other chromatid a message and then have the last person in each chromatid relate his or her correct/incorrect message at the end of the replication.

You may consider "planting" students with special messages to simulate certain types of mutations. Feel free to use your imagination to modify and improve this lab.

The Woodrow Wilson National Fellowship Foundation

webmaster@woodrow.org
CN 5281, Princeton NJ 08543-5281

Tel:(609)452-7007

Fax:(609)452-0066