DNA Extraction Lab
Introduction
DNA is a long thin molecule found in the nucleus of all living cells. The structure of the DNA
molecule gives it the ability to self-copy and carry instructions for the formation of protein. It is
what genes are made of. This Strawberry DNA extraction activity results in a large quantity of
white DNA. Strawberries (Fragaria ananassa) work well because they produce chemicals that aid
in the breakdown of cell walls plus they have 8 (yes, eight!) of each type of chromosome, whereas
we only have 2 of each chromosome.
Purpose
To separate DNA from the other components of living cells so that the DNA is tangible and can be
seen. Similar steps and reagents are used in research labs to purify DNA for genetic analysis and
sequencing.
Materials per Partnership/Two students
One Ziploc bag
One strawberry
DNA Extraction Liquid
Wood Stirring Rod
Cold Ethanol (keep iced) Graduated cylinder + rack to hold it
Filtering apparatus (cheesecloth, funnel)
Petri Dish (optional, to place spooled DNA)
Procedure
1. Obtain a strawberry from your teacher or stock lab station. Remove all leaves from strawberry if necessary.
2. Place the strawberry in the Ziploc bag and smush (gently) for one minute. Completely crush the strawberry (the less
bubbles the better). Be careful not to tear the bag.
3. Place 10mL of the DNA Extraction Liquid into the bag. The detergent in the soap helps dissolve the phospholipid
bilayer of the cells while the salt helps separate the protein in the extract layer so the DNA can separate from it.
4. Smush the mixture in the bag for one minute. Again, the less bubbles the better.
5. Use the Filtering Apparatus (funnel with cheesecloth over it) to pour the mixture over the graduated cylinder. Filter 3
– 4mL of the liquid into the test tube.
6. Add to the filtered strawberry solution by filling the graduated cylinder to 8.5mL with cold ethanol provided (keep on
ice). You may have to share the ethanol with a neighboring group.
7. Let the ethanol and strawberry solution sit for a minute. Then, gently swing the graduated cylinder to allow the
solutions to mix better. Watch for the development of several large air bubbles that have a white cloudy substance
attached to them. The cloudy substance is DNA!!
8. Use a wooden stirring rod (coffee stirrer) and spin/stir it VERY GENTLY like you’re making cotton candy. Tilt the test
tube to access more DNA and continue to gently “spool” it.
9. Pull out the DNA attached to the wooden stirring rod and place it on your Petri dish. It will look like mucus or egg
white (or snot!). As it dries, it will look like a spider web. The fibers are millions of DNA strands. Wanna keep it??  See
me!
10. Rinse out bag, stirring rod, test tube, etc (to reuse) and clean up your lab station entirely and work on the Debrief
Questions.
Debrief Questions (copy down and complete in journal).
1.
2.
3.
4.
5.
6.
What does spooled DNA look like?
A person cannot see a single cotton thread 100 feet away, but if you wound thousands of threads together into a
rope, it would be visible. What analogy is being represented here (i.e., what is the “rope”)?
In order to study genes, scientists must extract DNA from human tissue. Would you expect the method of DNA
extraction we used for strawberries to be the same for human DNA? Why or why not?
Is the DNA the same in any cell of the human body? Explain why or why not.
Think of two reasons (and list them) why a scientist might want to study the DNA of strawberries.
Think of two reasons why a scientist might want to study the DNA of humans.