Name: ______Date: ______Class:______
DNA Keychain
In this activity you will make a keychain out of beads and twine to resemble a small portion of the double helix DNA molecule. Bring your colored pencils to class!
1. You will be given the sequence of nitrogen bases for the left side of the molecule and will need to determine the correct corresponding sequence for the right side. Be sure to color the bases correctly. Adenine=Red Cytosine=Yellow Guanine=Blue Thymine=Green
Left side of molecule:
Right side of molecule:
MUST be signed off by teacher BEFORE proceeding to the next step.
2. Count the number of each color bead you will need and record here:
_____ Red ____ Yellow _____Blue ____Green
3. Get your supplies for the model (twine and the correct number of each color bead). You will also need 16 white beads and 16 black beads.
4. Bend the twine into a “U” shape, slip on the first base pair using the correct color beads AND the sugar (white bead) molecules. These beads should be at the bottom of the “U”.
5. Secure the first pair by looping the opposite string through the colored beads and sugar molecules. Watch the demonstration on the screen! Center the beads on your string and pull tight. This first pair will look slightly awkward.
6. Add a phosphate (black bead) to each side.
7. Slip on the second base pair using the correct color beads AND the sugar (white bead) molecules.
8. Secure the second pair my looping the string through the colored beads and sugar molecules. Center the beads on your string and pull tight. This second pair will look more like a “step” on the ladder.
9. Add a phosphate (black bead) to each side.
10. Continue in this manner until all 8 base pairs in place. Tie the ends together at the top.
Give your model a gentle twist to see the double helix. Add a “ring” to form the keychain.
Take your DNA keychain and this paper to your teacher for your final grade.
Teacher: Does keychain match the sequence? ____ Grade: ______