- Tell students that today they will be assembling a DNA puzzle. Show students each of the pieces and tell them what the letters on each represent. If you want, tell students the beginning of the DNA discovery story, especially how Watson and Crick created puzzle pieces to represent the different parts and tried to fit the pieces together in a way that made sense with the data that was known at the time.
- Pass out the puzzle pieces and instruct students to build a DNA molecule. Very little instruction is needed since it is very difficult to put together wrong. The only errors I’ve seen are students who try to flip the pieces so that the letters are hidden and students who try to fit the triangle indent of “T” with the triangle point of “S”.
- Circulate around the room and help students as needed. When most students have assembled a molecule 4-5 base pairs long, have students start connecting their molecule together with their neighbors’. At this time, they should also begin taping their molecules together with Scotch tape.
- When all the students have merged their pieces into a single long strand, have several students hold up the assembled molecule at the front of the class. Draw conclusions and observations from the group. For instance:
- What do you notice about the structure overall? What does it look like?
- How do the two sides of the ladder compare?
- What are the rungs of the ladder made of?
- Which nucleic acid pairs with which?
- How were each person’s individual DNA the same as others’ DNA? How were they different? In what ways you think the real DNA in each person’s cells is the same? In what ways do you think it is different?
- Relate the activity back to the real story of the discovery of the DNA structure.
- Complete the discussion with a formal definition of the vocabulary words such as base pair and nucleotide.
- Optional: “Laminate” the models by covering both sides of the model with packing tape. The model may then be twisted into a helix and hung from the ceiling or walls of the room. You may want to hold off on laminating your model until after discussing DNA replication, transcription, and translation (see Going Further ideas).
Laminated DNA paper puzzle