Unit 6 - Molecular Genetics
Name________________________________ Date_______
Strawberry DNA Extraction Lab (10pts)
DNA is inside the cells of every living thing. We have learned about
DNA, but have you ever seen it? With the Strawberry DNA experiment, you'll
extract, isolate, and observe the DNA of a strawberry in a matter of minutes. It sounds
impossible, but thanks to the special characteristics of strawberries, it's actually very
possible. Strawberries are octoploid, meaning that their cells each have eight duplicate
copies of each chromosome. This gives the cells a lot of DNA, which means it is easier to
extract a large amount of DNA that is visible to the naked eye. You don't have to be a
geneticist. It's easy, fun, and all you need are some household materials.
MATERIALS
Strawberry
Isopropyl alcohol (5mL)
Dish Soap (10 mL)
Zip-Lock Bag
gauze
water
Beaker
Stirring rod
salt
EXPERIMENT
1. Obtain a strawberry and place it in a ziploc bag. Take most of the air out of the
bag and seal it.
2. Mash the strawberry with your hands. Be careful not to break the bag.
3. Add the DNA extraction solution to the bag. Just enough to cover the bottom of
the bag. (Solution is water, dish detergent and salt)
4. Reseal ziploc bag being careful to remove most of the air.
5. Mix the solution with strawberry mash for 1 minute.
6. Place a piece of gauze over the top of the plastic cup. Secure with a rubber band.
7. Pour strawberry mixture on top of gauze being careful not to spill.
8. When all liquid is drained remove gauze and throw in garbage.
9. Add isopropyl alcohol to liquid.
10. You should see a white thread-like cloud appear. This is the DNA of the
strawberry!
11. Gently remove the DNA from the solution using tweezers and observe.
12. Show your DNA strand to your teacher before discarding and cleaning up.
Unit 6 - Molecular Genetics
BACKGROUND INFORMATION
Why do we use dishwashing liquid?
The dishwashing liquid dissolves the lipid part of the strawberry cell wall and nuclear
membrane.
Why do we use salt?
The salt breaks open the protein chains that bind around the nucleic acids.
What does the alcohol contribute to the experiment?
When molecules are insoluble (unable to be dissolved), they clump together and become
visible. DNA is not soluble in alcohol; therefore, the DNA strands clump together and
become visible to the naked eye.
Conclusions and Analysis
1. It is important that you understand the steps in the extraction procedure and why
each step was necessary.
Each step in the procedure aided in isolating the DNA from other cellular materials.
Match the procedure with its function: (4 pts)
PROCEDURE
FUNCTION
A. Filter strawberry slurry through cheesecloth
solution
___ To precipitate DNA from
B. Mush strawberry with salty/soapy solution
___ Separate components of the cell
C. Initial smashing and grinding of strawberry
___ Break open the cells
D. Addition of ethanol to filtered extract
___ Break up proteins and dissolve
cell membranes
2. What did the DNA look like? Relate what you know about the chemical structure of
DNA to what you observed today. (1 point)
Unit 6 - Molecular Genetics
3. Explain what happened in the final step when you added alcohol to your strawberry
extract. (1 point)
5. Why is it important for scientists to be able to remove DNA from an organism? (1
point)
6. Is there DNA in your food? ________ How do you know? ( 1 point)
7. Where is DNA located in Eukaryotic cells? Where is it in prokaryotic cells? ( 2 points)