How can you extract the DNA out of a strawberry (Fragaria × ananassa)?

Introduction (Matt)

This experiment is about extracting DNA out of a strawberry, although this can be accomplished on a large amount of fruits (i.e. bananas, kiwis, blueberries). There are a number of reasons why people would conduct this experiment, setting just curiosity aside. This is most commonly done at the college undergraduate level as a general biology experiment, teaching students about genomics in a very cost-effective manner. Why is this most commonly done with strawberries? Ripe strawberries are an excellent source for DNA extraction because they have eight copies of each chromosome, also known as octoploid, leaving a lot of DNA to isolate. Additionally, they are easy to pulverize and contain enzymes called “pectinases and cellulases that help to break down cell walls” (Sweeney). This experiment also uses common household items, which will be discussed by Brandon, leaving opportunities for almost anyone to conduct this at home.

Methods (materials/procedure) (Brandon)

Measuring cup
Measuring spoons
A resealable plastic bag
2 strawberries (fresh or frozen, but remove the green leaves)
2 tsp. dish detergent
tsp. salt
½ cup water
2 plastic cups
1 coffee filter
½ cup cold rubbing alcohol
Popsicle stick or toothpick

Experimental Procedure

1. Place strawberries in a plastic bag. After closing the bag, smash the strawberries for ~2 minutes.
2. Make a DNA extraction solution by adding the following to the first plastic cup:
– 2 tsp. dish detergent
– 1 tsp. Salt
– 1/2 cup water
3. After gently mixing the extraction solution (until salt is dissolved), pour it into the bag of smashed strawberries.
4. Reseal the bag and gently massage and mix the mixture for a minute. Try to avoid making too many soap bubbles.
5. Place the coffee filter over the opening of the second plastic cup. open the plastic bag, and pour the liquid onto the coffee filter. Then wait for the liquid to drip through the coffee filter into the plastic cup, leaving the strawberry mush on the coffee filter.
6. Pour an equal amount of cold rubbing alcohol into the liquid in the second plastic cup.
7. Gently move the cup around in circles and watch the mucus-like material form in the upper layer of liquid — that is the strawberry DNA.
8. Use the popsicle stick or toothpick to pick up strawberry DNA out of the liquid.

Results/Observations (Zulfa)

During the experiment, we were able to extract DNA from strawberries using common household items. We observed the following results:
● Smashing the strawberries in the plastic bag helped to break down the cell walls and release the DNA.
● The extraction solution containing dish detergent, salt, and water helped to break down the cell membrane and nucleus, allowing the DNA to be released into the liquid mixture.
● Pouring the liquid mixture onto a coffee filter helped to separate the liquid from the solid strawberry mush.
● Adding cold rubbing alcohol to the liquid mixture helped to cause the DNA to precipitate out of the solution and form a snot-like material in the upper layer of the liquid.
● The extracted DNA appeared as a white, stringy substance that could be picked up using a popsicle stick or toothpick.
Overall, the experiment successfully demonstrated how DNA can be extracted from strawberries using simple household items. This experiment can be used to introduce students to basic concepts of DNA structure and extraction techniques.

Conclusion (Amy)

To conclude, the extraction of strawberry DNA can be easily conducted in a home or classroom setting. This experiment provides the opportunity to observe the physical characteristics of DNA but also understand the importance and properties of DNA in different living organisms. The importance of this experiment is to study and manipulate the DNA to create new fruits. Additionally, this experiment gives a base understanding of molecular biology and genetics to students from all ages. Some errors and biases that have occurred during the experiment that could affect the results are the salt and soap in the solution if it was not completely mixed it would not break up the proteins giving less product. the amount of Ethanol if it was less than ½ cup the precipitation of DNA from the solution could be altered (clump the DNA together).

References
– Strawberry DNA Extraction. (n.d.). Genome.gov. https://www.genome.gov/about-genomics/teaching-tools/strawberry-dna-extraction
– Sweeny, D. (n.d.). DNA Isolation from Strawberries. In University of Washington. https://www.gs.washington.edu/outreach/dhillon_dnaprocedure.pdf