DNA Lab

FRAMEWORK
I.Scientific and Engineering Practices
II.Cross-Cutting Concepts
III.Physical Sciences
SKILLS/OBJECTIVES
  • Learn the components, structure and function of DNA

  • Learn how to Extract DNA

MATERIALS
  • DNA model kit
  • Red and black hollow licorice sticks
  • Gummy bears
  • String
  • Toothpicks
  • Small white marshmallow
  • Red, green, yellow, blue beads
  • Bracelet string
  • DNA extraction kit
  • Fruits or other living things to extract DNA from

Activity # 1 / DNA MODEL
Materials / Kit
Worksheet / Y/N

  • What is DNA? What does it do? Why is it important?
  • What are the different parts? (use pre-made model) How do they fit together?
  • Introduce vocabulary (deoxyribonucleic acid, nucleotides, double helix)
  • Using the pre-made model as a guide, build the model from the kit as a demo. Ask kids what individual pieces are & where they think they will go before actually putting the whole thing together. Explain the basic functions of each part as you put it in the model (i.e. “What do you guys think this is? It’s a nucleotide! And what do you think it does? They go in different pairs to tell your cells what to do! And where do you think it goes in the model? Right here!”)

Activity # 2 / Gummy double helix
Materials /
  • Gummy bears
  • Toothpicks
  • Twizzlers

Worksheet / N

NOTE: DO NOT EAT THE FOOD

Split into smaller groups with one or two volunteers per group. Tell the kids they will be replicating the model from the demo with candy. Ask the kids what they think each type of candy will correspond to which DNA component (What part of DNA does this look like?) in order to reinforce vocabulary before assisting them in building the models.

What To Do:

  1. Gather together four different colors of gummy bears, the Twizzlers, and the toothpicks.
  2. Cut the twizzlers into strips roughly one inch long.
  3. Pair two colors of the gummy bears together and then pair two other colors together. (These stand in for the different pairs of nucleotides!) For example, red and orange gummy pairs could be paired together, and green and yellow ones be paired together.
  4. Take a gummy bear and thread it onto the toothpick. Thread the complementary gummy bear onto the toothpick so that they are on opposite ends of the toothpick.
  5. Repeat step five to make another gummy bear toothpick, this time using the pair of colors you did not use before.
  6. Between these two pairs of bears, stick two toothpicks with a piece of twizzler on them (this stands in for the sugar backbone) and attach to the bears.
  7. Repeat once or twice, then pick up the structure and twist slightly in midair to give it the double helix look. Viola, DNA!

Activity # 3 / BEAD DNA SQUENCE BRACELET
Materials / Elastic/string for bracelets
Red, green, yellow, blue beads
Worksheet / N

Just like in DNA, there are four different kinds of units that make up the sequence - red, green, yellow and blue. Your bracelet will contain two strands of beads that match up the same way the units (or bases) in DNA do. Each base will match up with a different bead color.

  • Have several different sequences (monkey DNA, dog DNA, horse DNA, etc.) on index cards, and tell the kids to choose an animal they like and copy its DNA sequence with their bracelet

Choose one DNA sequence to make.

  1. Find or cut two pieces of elastic each about 30 cm long.
  2. Tie a knot about 5 cm from one end of each string; then tie the two strings together at the knots.
  3. Look at the first letter in your sequence and find the right color bead to thread.
  4. Thread that bead onto string 1 and thread the bead for the matching base onto string 2 (see the Pairing Rules sheet for guidance). Keep threading beads according to your sequence until you’ve finished the sequence on your card.
  5. Knot each string after the last bead, and then tie the two new knots together.
  6. Now tie the ends of your double-stranded sequence bracelet together.

Activity # 4 / DNA EXTRACTION KIT
Materials / 1 resealable plastic bag
Strawberries (fresh or frozen)
2 teaspoons of dish detergent
1 teaspoon of salt
½ cup of water
2 plastic cups (One cup will be used for the filtering apparatus below)
Filtering apparatus: coffee filter and plastic cup
Ice cold 90 percent rubbing alcohol
1 wooden popsicle stick or plastic coffee stirrer
Worksheet / N



  • Explain what DNA extraction is; it is the process of taking the DNA out of the cell and observing it
  • Ask for some basic predictions – what color will it be? Will we be able to see it?

1. Pull off any green leaves on the strawberry that have not been removed yet.

2. Put the strawberry into the plastic bag, seal it and gently smash it for about two minutes. Completely crush the strawberry. This starts to break open the cells and release the DNA.

3. In a plastic cup, make your DNA extraction liquid: mix together 2 teaspoons of detergent, 1 teaspoon of salt and ½ cup of water.

4. Add 2 teaspoons of the DNA extraction liquid into the bag with the strawberry. This will further break open the cells.

5. Reseal the bag and gently smash for another minute (Avoid making too many soap bubbles).

6. Place the coffee filter inside the other plastic cup.

7. Open the bag and pour the strawberry liquid into the filter. You can twist the filter just above the liquid and gently squeeze the remaining liquid into the cup.

8. Next, pour down the side of the cup an equal amount of cold rubbing alcohol as there is strawberry liquid. Do not mix or stir. You have just isolated the DNA from the rest of the material contained in the cells of the strawberry.

9. Within a few seconds, watch for the development of a white cloudy substance (DNA) in the top layer above the strawberry extract layer.

10. Tilt the cup and pick up the DNA using a plastic coffee stirrer or wooden stick.

  • Ask how we can see so much DNA when the cells it’s in are so small (it’s curled up very tightly)