Curriculum topics:
 Biology
 Molecules
 Cell Structure
 Genetics
 Scientific Tools
 Lab Procedures
Subjects:
Life Science,
Physical Science
STRAWBERRY DNA
ILLUSTRATED
Build student interest with this simple DNA
activity!
Grade range: 4– 12
Use ordinary dish soap, salt, and isopropyl alcohol to extract DNA from
strawberries. Just follow the illustrated guide. No special skills or
equipment required.
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Purchase:
Strawberries
Prepare:
Fill container
with water
Dish soap
Put alcohol
in freezer
Salt
Isopropyl
alcohol
Tape funnels
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© 2014, RAFT
http://www.raft.net/raft-idea?isid=677
Materials required
Per student or team:


Ripe strawberry, or frozen strawberry,
completely thawed
Resealable plastic bag, snack or
sandwich size
Water, 20 ml (4 teaspoons)
Dish soap, 2 ml (½ teaspoon)
Salt, ~ 1 ml (~1/4 teaspoon), non-iodized
Isopropyl alcohol, 5 ml (1 teaspoon)
(ethanol will also work)




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Test tube or similar narrow clear container that
will hold ~25 ml (5 teaspoons)
Small funnel or paper cone that fits in test tube
Small piece of open weave cloth, 10 cm (4”)
square
Thin wooden stir stick or skewer
Teaching Tip: Remind students not to
eat or drink while doing science labs.
How to build it
Safety Message: This activity uses isopropyl alcohol. Adult supervision is required.
Isopropyl alcohol is flammable. Keep away from heat and open flame. Avoid prolonged
exposure. Wear eye protection when handling isopropyl alcohol.
Wash hands thoroughly using soap and water after handling.
Dispose of isopropyl alcohol in accordance with federal, state and local regulations.
1
Remove the sepal (green part) from the strawberry as shown at right:
2
Put 1 strawberry, 20 ml (4 tsp) water,
2 ml (½ tsp) dish soap, and 1 pinch of salt in the bag.
Firmly seal the bag.
3
Thoroughly mash the contents by squeezing the
bag with your fingers for 2 minutes.
SQUISH
SMOOSH
SQUASH
4
Form the index card into a funnel and tape it as shown below. Be sure to leave a hole at the
bottom of the cone.
5
Press the cloth into the cone as shown at right.
Strawberry DNA Illustrated, page 2
© 2014, RAFT
6
Pour the liquid from the bag into the funnel.
Give it time to seep through the cloth into
the tube. Try to get all of the liquid out of the bag;
it is not nessary to transfer all of the solids.
7
Remove the alcohol from the freezer
and carefully pour 5 ml (1 tsp) into
the test tube by tilting the tube and letting
the alcohol run slowly down the side, as shown.
8
Notice the cloudy white
strands of DNA that collect
in the alcohol.
Alcohol
DNA
Water
Gently wind the DNA material around the stir stick.
8
To do and notice
1
2

Look closely at the clumps of DNA. Describe the clumps. Notice how the DNA sticks to itself.
Might its appearance be related to its double helical (spring-like) structure?
Compare results and share observations with other students. Did everyone extract the same
amount of DNA? If not, make some guesses about what might have caused the variations.
The science behind the activity
All living things contain DNA. Strawberries are a great source of DNA because every cell contains eight
copies of each chromosome (octoploid). For comparison, human cells only contain two copies.
Strawberry DNA Illustrated, page 3
© 2014, RAFT
Curriculum
Standards:
The science behind the activity (cont’d)
Each ingredient in the experiment performs a special function:
Molecules
(Next Generation
Science Standards:
Middle School,
Physical Science 1-1)
Cells
(Next Generation
Science Standards:
Middle School, Life
Science 1-1 & 1-2)
Science & Engineering
Practices
(Next Generation
Science Standards:
Grades 4 – 12)
•
Dish soap breaks down the cell membrane so the DNA can escape.
The soap molecules do this by breaking the bonds between the
phosphates and fatty acids in the cell membrane.
•
Salt helps to purify the DNA by breaking up the protein chains and
keeping them from binding around the DNA molecule. The proteins
stay in the water.
•
DNA does not dissolve in water or alcohol because it is non-polar.
Instead it forms “clumps” at the boundary between the two liquids.
One strand of DNA is much too small to see with the naked eye or even with a
powerful microscope. The small clumps that are formed in this experiment
each contain thousands of long strands of DNA which are all tangled together.
Learn more

Try this experiment using bananas, kiwi fruit, oatmeal, or other living
materials. Compare the amount of DNA extracted from samples of the
same weight.

Use this activity to introduce biological terms such as genome,
chromosome, cell wall, solubility, extraction, and purification.
Related activities: See RAFT Idea Sheets:
Codon Necklaces http://www.raft.net/ideas/Codon Necklaces.pdf
Modeling DNA http://www.raft.net/ideas/Modeling DNA.pdf
Who’s the Daddy? http://www.raft.net/ideas/Who is the Daddy.pdf
Who’s Your Mummy? http://www.raft.net/ideas/Who is Your Mummy.pdf
Resources
Visit www.raft.net/raft-idea?isid=677 for “how-to” video demos & more ideas!
See these websites for more information on the following topics:
Additional standards at:
http://www.raft.net/raftidea?isid=677

Understanding Genetics: Stanford at The Tech Museum of
Innovation - http://genetics.thetech.org/

Resources on DNA from CK-12 - http://www.ck12.org/concept/DNA-theGenetic-Material/#all

Video on DNA from the Khan Academy –
https://www.khanacademy.org/science/biology/evolution-and-naturalselection/v/dna
9999
Strawberry DNA Illustrated, page 4
© 2014, RAFT