Make & Take Activity – Strawberry DNA Necklace

1. Tell youth you are thinking of a specific food, you are going to give them a list of clues, and you want them to guess which food you are thinking of. Ask students to wait until the end of your clues to share an answer.
   • This food comes from a perennial plant. This food has seeds on the outside. This food is fruit. This food is usually red but can also be yellow or white. What is this fruit? Strawberries!
2. Explain to youth that strawberries are usually red but can also be yellow or white. This is because of genetics and traits. Each strawberry has unique DNA and variations in DNA lead to different characteristics (colors). Is there DNA in my food? Absolutely! DNA can be seen with the naked eye when collected from thousands of cells. Strawberry farmers and plant breeders work together to create varieties of strawberries that meet our needs using DNA. Today, students will extract DNA from a strawberry.

1. Divide youth into groups of three or four and provide each group with the following materials: sandwich bag containing three strawberries and three tablespoons of DNA extracting solution (1/2-gallon water, ½ cup clear dish soap, 2 tbsp salt), funnel, plastic cup, 2 squares of cheesecloth (4”x4”), graduated test tube, pipette, 3–4 microcentrifuge tubes (1 per student), and 3-4 pieces of yarn (1 per student).
2. Carefully remove most of the air from the bag, and seal it well.
3. Gently mash the strawberries in the bag. Be careful not to break the bag. Be sure to mash the strawberries thoroughly.
4. Place the funnel in the plastic cup. It should sit on the rim of the cup.
5. Place the two squares of cheesecloth into the funnel, forming a liner for straining.
6. Carefully pour the strawberry mixture into the funnel, making sure to catch the solids with the cheesecloth. After filtering the mixture, remove the cheesecloth, and place it into the bag for disposal.
7. Add 5 ml of the filtered strawberry extract to the graduated test tube using the funnel. Hold the tube near the top so that the heat from your hand does not affect the extraction.
8. Remove the funnel and use the pipette to forcefully add 3 ml of the rubbing alcohol to the test tube. Take care not to tilt or tip the test tube; do not mix the two liquids together.
9. Observe the line between the strawberry mixture and the alcohol. You will notice a white, thread-like cloud appearing at this line. This is the strawberry DNA. The DNA will clump together and float to the top of the alcohol layer.
10. Holding the tube still, observe the tubes of others around you. Do you notice any differences?
11. Using the pipette, add some DNA strands and some of the alcohol in the test tube to each person’s microcentrifuge tube. Repeat steps 6 to 8 if necessary to collect enough DNA for everyone’s microcentrifuge tube.
12. Close the cap of the microcentrifuge tube tightly around a piece of yarn and tie the ends of the yarn to make a necklace.
13. Clean up! Dump the remaining strawberry solution where instructed, throw away the bags, and collect the cups, test tubes, funnels, and pipettes to clean so they can be used again.

Like all living things, every plant and animal used in agriculture has DNA. The process of DNA extraction is an important component of agricultural biotechnology, allowing to select for desirable traits more accurately.