Today we will learn how to extract DNA from strawberries. This is a fun activity to do with kids of all ages and teaches them about DNA.
Why Strawberry?
Strawberry plants are octoploids, meaning they carry eight copies of each chromosome. To put this in perspective, humans are diploid carrying only 2 copies of each chromosome. In other words, strawberries have a lot of DNA. Considering this fact along with the availability and softness of strawberries, the fruit is the perfect contender for this at-home DNA Extraction.
Supplies
- Strawberry
- Lysis buffer
- Cheese cloth
- Disposable Pasteur pipette
- Wooden stick
- Collection tube
- Ribbon
- Ethanol
- Small Ziploc bag
- 2 ml microcentrifuge tube
How to prepare Lysis Buffer:
- Add 45 mL of water to a 50 ml conical tube.
- Add 5 mL of detergent and 2 tsp of salt to the water.
- Shake the mixture well before use.
Step 1: Make Strawberry Lysate
Place one whole strawberry in a Ziploc bag. No need to remove the leafy top. Add 10 ml of the prepared Lysis Buffer into the bag. Remove all the air and then seal the bag. Smash the strawberry into a nice pulp.
You have prepared a strawberry lysate i.e. strawberry cells that have been broken down.
Function: The purpose of the lysis buffer is to destroy the fatty membranes that encapsulate organelles that hold DNA. The salt further frees the DNA by ridding it of the associated proteins.
Step 2: Filter the Strawberry Lysate
Set a funnel in a clear collection cup (beaker or glass jar) and place a piece of cheesecloth in the funnel. Tip: double fold the piece of cheesecloth to better separate the fruit bits from the liquid.
Making a small opening in the ziplock bag, start pouring contents into the funnel. Be careful not to overfill the filter.
Let the liquid drain into the cup. To collect more liquid, gently squeeze the cheesecloth. You have successfully produced a filtrate with strawberry DNA.
Step 3: Visualize your Strawberry DNA
In the collection cup, add 3 mL of ethanol using a disposable pipette. The pipette is not essential, so if you are pouring in the ethanol, make sure to pour it slowly. Cold ethanol is recommended, however, room-temperature ethanol works well too.
You will begin to see a layer of cloudy precipitate on top of the strawberry lysate. This cloudy residue is the DNA!
Function: Ethanol separates DNA from the solution because DNA is not soluble in Ethanol.
Step 4: Collect DNA
Gather the DNA using a wooden stick (a toothpick will also work) and transfer it to a 2 mL centrifuge tube.
Conclusions
The DNA is safe for the kids to take home in the tubes seeing that harmful chemicals were not used. But do not stop here! Add some string/ribbon to make necklaces. Or continue the experiment by performing PCR and gel electrophoresis.
DNA extraction is a vital method used in laboratories to identify anything from plants like a strawberry to chronic illnesses such as cancer. Strawberry DNA extraction is an exciting experiment to bridge the microscopic world to the macroscopic world.