Fruit Loops

Which Fruit Will Yield the Most DNA?

By using things that you find in your house or at the local grocery store, you can see DNA! Below is a list of steps for taking the DNA out of different fruits. What do you think it will look like?

What is DNA?

DNA is the single most important molecule in living cells and contains all the information that determines who you are, what you look like, and how you develop and function. You are made up of billions of cells and each cell has its own unique set of 46 chromosomes. These chromosomes hold, as a compressed coil, an incredibly long molecule of DeoxyriboNucleic Acid, or DNA for short. This DNA contains all the coded information that makes you the remarkable person you are!

While the DNA molecule is very long, it is also surprisingly simple. Actually, DNA can be pictured as an incredibly long ladder that has been twisted into a double helix shape that looks something like this:

The chemical compound DNA was first discovered by Friederich Miescher in Germany about 100 years ago. Francis Crick and James Watson, discovered the 'Double Helix' structure in 1953.

You can find more facts about DNA, chromosomes and molecules, on the Biotechnology Institute website at www.biotechinstitute.org

Activity Time

25 minutes

What You Need:

• Table salt
• Soap such as liquid hand soap (Ivory) or liquid dishwashing detergent, such as Palmolive
• Tap water
• 91 or 99% rubbing alcohol (You will have to go to the grocery store or drug store for this most likely.)
• 3 different fruits of your choice, such as strawberries, kiwi, and cherry tomatoes.
• 3 coffee filters or 3 pieces of cheesecloth
• Small plastic funnel
• 3 clear medicine cups or any small clear container. You can find them on top of cough medicine or ask your local pharmacy for some.
• Eye dropper
• 3 Sandwich-size plastic resealable bags
• 3 DNA extractors made from paper clips – Open the clip to make a hook. You’ll use one side as the hook and the other as a handle.

What to Do?

1. Open up three plastic resealable bags. Mark them with the names of the fruits you use. We will use cherries, kiwi, and cherry tomatoes.
2. Put 4 cherries in 1 bag, a thick slice of Kiwi (about the size of the 4 cherries) in the second bag, and 2 small cherry tomatoes or a thick slice of a regular tomato in the last bag.
3. Zip all 3 bags shut.
4. Squeeze the bags in your hands one at a time to squish fruit. This helps to mash the fruit and break down the cell walls.
5. Add 3 squirts of liquid hand soap, a pinch of salt (about 1/8 teaspoon), and 2 droppers of water to each bag.
6. Squish the contents of the bags again to mix well.
7. Place a coffee filter or a piece of cheesecloth in a funnel over a medicine cup. Mark it cherries. Cut 1 corner of the bag off and squeeze the cherry slush into the coffee filter. Let it drip down into the cup. Now do the same with the other 2 fruits, marking the containers for each fruit.
8. Take the funnel off and throw away the filter paper.
9. Carefully pour 2 droppers full of rubbing alcohol slowly down the side of the medicine cup.
10. This is the step where you have to be patient. Wait 5 minutes and be careful not to move your cups.
11. You will see little bubbles form and rise to the top, followed by tiny white strings. The little white strings are DNA!
12. As soon as you see a good clump of DNA (it may take 10 minutes), use your DNA collector to gather DNA and carefully scoop it up. Use a slow twirling motion to avoid breaking and separating the strands. If you like, you can deposit the strands in clean medicine cups or lay them flat on a plate.
13. Visually compare how much DNA you were able to extract from each fruit. Can you tell which fruit has the most DNA? How does the DNA feel when you touch it?