Name _______________________________
Date ____________
Period ________
DNA Extraction Lab - Strawberries
Background:
DNA is the material of inheritance. The student will observe that DNA is found in
biological organisms such as a strawberry, and DNA has a threadlike appearance.
Materials per student group:
2-3 Fresh or individually frozen strawberries
1 Ziplock plastic freezer storage bag
10 mL DNA extraction buffer *
500 mL H2O, 20 mL dishwashing detergent (not antibacterial)
1/8 t salt
1 50 mL test tube
10 X 20 cm Double ply cheesecloth
10 mL Isopropyl alcohol
1 Plastic pipette
1 Wooden skewer
Procedure:
1. Place 2-3 strawberries in a Ziplock plastic freezer storage bag. Remove the air
from the bag, seal it, and thoroughly mash the contents in the bag with your hands.
2. Pipette 10 mL of the DNA extraction buffer into the Ziplock plastic freezer storage
bag. Remove the air from the bag, seal it, and mix the mashed strawberries and DNA
extraction buffer together.
3. Pour the strawberry mixture into the cheesecloth. Twist each end of the -cheesecloth
(Figure 1) and filter (strain) the mixture into the test tube. Use a funnel to facilitate
the
transfer from the cheesecloth containing the strawberry mixture to the test tube. Fill
¼
of the test tube (10-15 mL) with the strawberry mixture.
4. Remove the funnel from the test tube, and discard the cheesecloth with the leftover
strawberry mixture.
5. Use a pipette to drizzle 10 mL of isopropyl alcohol down the insides of the test tube
(Figure 2). The isopropyl alcohol should form a layer on top of the strawberry mixture.
A white, stringy precipitate containing DNA should begin to form (Figure 3).
6. Place the blunt end of a wooden skewer into the center of the test tube. Slowly rotate
(not stir) the skewer in one direction. The DNA should spool onto the wooden skewer
(Figure 4).
7. Write your observations about the DNA extraction.
Observation Notes:
Teacher Notes:
Internet demo video of strawberry DNA extraction:
www.coe.unt.edu/harrell/strawberryDNAextraction.htm
The teacher needs to prepare the following solutions before doing the lab:
Prepare an 8% soapy water solution by combining 250 mL H2O with 20 mL of
dishwashing detergent (not antibacterial) in a 750 mL beaker.
Prepare a 2% saltwater solution by combining 250 mL H2O with 1/8 t. salt in a 500 mL
beaker.
Transfer the 2% salt-water solution to the 750 mL beaker and mix the two solutions
together.
The soapy salt-water solution will function as the DNA extraction buffer.