Name ________________________________________
EXTRACTING DNA
FROM STRAWBERRIES
Period _______ Date ___________ Seat _______
Materials per student group
150-mL beaker
50-mL graduated cylinder
10-mL graduated cylinder
Test tube (1.5cm x 15cm) (1)
Funnel lined with moistened paper towel
Ring stand with ring
Toothpicks (2)
Glass stirring rod
35-mL of strawberry puree
10-mL of DNA Extraction Buffer
8-mL of ice-cold isopropyl alcohol
Wax paper (5cm x 5cm)
Microscope
50mL Graduated
Slide and coverslip
cylinder
Directions
1. Add 35-mL of strawberry puree to a 150-mL beaker.
Figure 1
Buffer
Beaker
2. Add 10-mL of DNA Extraction Buffer to the beaker.
3. Use a stirring rod to gently stir the strawberry/buffer mixture
for 1 minute. Try not to make soap bubbles. See Figure 1.
4. Filter through a moistened paper towel set in a funnel, and
collect 10-mL of strawberry liquid in the 10-mL graduated
cylinder. Do not squeeze the paper towel. See Figure 2.
5. Throw away the paper towel. Rinse out the beaker.
Stirring
rod
Strawberry
Puree 35-mL
Beaker
Figure 2
Strawberry
Puree
Paper Towel
6. Transfer the strawberry juice from the 10-mL graduated
cylinder to the test tube. Use the beaker as a test tube holder.
7. Add 10-mL of ice-cold isopropyl alcohol. Pour the alcohol
carefully down the side of the test tube so that it forms a
separate layer on top of the strawberry liquid. See Figure 3.
8. Watch for about a minute. What do you see? You should
see a white fluffy cloud at the interface between the two
liquids. That’s DNA! See Figure 4.
9. Spin and stir the stirring rod in the tangle of DNA, wrapping
the DNA around the stirrer. See Figure 4.
Funnel
10mL Graduated
cylinder
Figure 3
8-mL Isopropyl
alcohol
10. Pull out the stirrer and transfer the DNA to a piece of wax
paper. The fibers are thousands and millions of DNA strands.
11. To view in a microscope, put the glob on a clean slide and gently
tease/stretch apart using 2 toothpicks. Add a drop of water and
a coverslip. The fibers will be easier to see in the teased-apart
area.
Clean Up
 Rinse your funnel and clean and dry the microscope slide.
 Place the equipment back where you obtained it.
 Wash and dry your work bench.
1
Test tube
Filtered
strawberry
Figure 4
Stirring rod
DNA
Isopropyl
alcohol
Filtered
strawberry
Interface
(were DNA
will appear)
Name ________________________________________
EXTRACTING DNA
FROM STRAWBERRIES
Period _______ Date ___________ Seat _______
Pre-Lab Questions
1. What do you think the DNA will look like?
2. Where is DNA found in an organism?
Conclusions and Analysis Questions
1. What did the DNA look like?
2. Relate what you know about the chemical structure of DNA to what you observed today.
3. What is the function of DNA?
4. Would the DNA be the same in any cell in the human body?
5. 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 much further away. Is this statement
analogous to the DNA we extracted?
6. Is there DNA in your food _________. How do you know?
2
Name ________________________________________
EXTRACTING DNA
FROM STRAWBERRIES
Period _______ Date ___________ Seat _______
Teacher notes
Per class (15 stations)
Buffer preparation:
250-mL water + 14-mL dishwashing detergent (or 100-mL shampoo) + 4 g NaCl
(or another formula)
900-mL water + 100-mL Dawn Dishwashing detergent + 20g salt
Strawberry puree:
Place 15 strawberries in a blender and add 500-mL water. Puree the mixture for 1 minute.
Other
Strawberry species and hybrids can be diploid, tetraploid, pentaploid, hexaploid, heptaploid,
octoploid, or decaploid. The “common strawberry,” or Fragaria ananassa is octoploid (8 sets),
having 56 chromosomes (7 chromosomes per set).
Bananas are triploid (33 chromosomes)
DNA Extraction virtual lab
http://learn.genetics.utah.edu/content/labs/extraction/
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