Name: ____________________________________
Date: _____________________
DNA Extraction from Strawberries Pre-Lab Notes
(Use when completing Criterion C part in Lab)
1. In eukaryotic cell, where is DNA found? _________________________________________
2. How is DNA extraction used in laboratories? ______________________________________
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3. Each human cell has about _______ feet of DNA.
4. Why are strawberries so good to use for extracting DNA? ___________________________
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5. What are cell membranes composed of? __________________________________________
6. What must be used to remove the phospholipids? __________________________________
7. What does the salt do to aid us in visualizing the DNA? _____________________________
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8. Without the salt, could we see the single DNA strands? Why? ________________________
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8. DNA will ________________ dissolve in alcohol, but it will dissolve in ________________.
8. Why should the alcohol and test tube with DNA be kept cold? ________________________
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9. What is the purpose of filtering the solution? ______________________________________
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10. Adding cold alcohol causes DNA to ______________ or separate from the solution.
11. DNA appears as a ___________ precipitate when alcohol is added.
12. Explain spooling. __________________________________________________________
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Name: _______________________________
Date: ________________
Strawberry DNA Extraction Lab (Criterion B and C)
Introduction: Deoxyribonucleic acid, or DNA, is found in the cells of all living organisms.
DNA can be extracted and isolated from any type of cell by a simple technique. After extracted,
DNA strands of DNA can be seen by the naked eye.
Criterion B:
Purpose: To extract DNA from a living organism (strawberry)
DNA is extracted for many purposes. These include the following: ___________________
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Independent Variable: __________________________________________________________
Dependent Variable: ___________________________________________________________
Controlled Variables: ___________________________________________________________
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Hypothesis: If ________________________________________________________________
then_________________________________________________________________________
because______________________________________________________________________
Materials:
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Rubbing alcohol
Plastic cup and plastic canister
Coffee filter
Resealable plastic sandwich bag with two strawberries
Bamboo skewer
Extraction liquid (one half teaspoon of salt, one third cup of water and one tablespoon of dishwashing
liquid)
Procedure:
1. Remove and discard the green tops from the strawberries.
2. Put the strawberries into a resealable plastic sandwich bag and push out all of the extra air. Seal the bag
tightly.
3. With your fingers, carefully and slowly squeeze and smash the strawberries for two minutes. How do
the smashed strawberries look?
4. Add three tablespoons of the extraction liquid you prepared to the strawberries in the bag. Push out all
of the extra air and reseal the bag. How do you think the detergent and salt will affect the strawberry
cells?
5. Squeeze the strawberry mixture with your fingers for one minute. How do the smashed strawberries
look now?
6. Place the coffee filter over the cup and have two group members hold the filter around the edges of the
cup. Slowly pour the strawberry mixture from the bag into the filter. Let it drip through the filter and
into the cup until there is very little liquid left in the filter (only wet pulp remains). How does the
filtered strawberry liquid look?
7. Pour the filtered strawberry liquid from the cup into the small test tube so that it is one eighth full.
8. Tilt the jar and very slowly pour the alcohol down its side. Pour until the alcohol has formed
approximately a one-inch-deep layer on top of the strawberry liquid. You may not need all of the cup of
alcohol to form the one-inch layer. Do not let the strawberry liquid and alcohol mix.
9. Study the mixture inside of the jar. The strawberry DNA will appear as gooey clear/white stringy
stuff. Do you see anything in the jar that might be strawberry DNA? If so, where in the jar is it?
10. Dip the bamboo skewer into the jar where the strawberry liquid and alcohol layers meet and then pull
up the skewer. Did you see anything stick to the skewer that might be DNA? Can you spool any DNA
onto the skewer?
Post-Lab Questions:
1. Where is DNA found in the cell? ______________________________________________
2. Discuss the action of the dishwashing soap on the cell. What is the purpose of the soap in
this activity? _______________________________________________________________
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3. What is the purpose of the Sodium Chloride (NaCl = salt)?
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4. Why was the cold ethanol added to the extraction liquid?
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Criterion C: (Use this section to help complete the rest of Criterion C)
Observations/Data: Sketch the test tube. What do you see and where? Label your diagrams.
1. Describe the appearance of your final product? Be detailed!!!
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2. Interpret your observations and results by describing your observations. Use scientific
vocabulary and reasoning to determine the product of your experiment.
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3. Restate your hypothesis. Was your hypothesis correct? How do you know? Give proof
based on your observations and the outcomes of the scientific investigation. Use scientific
vocabulary and the pre-lab questions to help answer this part.
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4. Validity of Method: Was the method you used a valid way to extract DNA? How do you
know? Give evidence by revisiting your variables. Was the independent variable the only
variable that could have affected the dependent variable? Were your other variables
controlled? Explain and use the information you learned in the pre-lab questions.
Use scientific vocabulary.
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5. Reflection: Describe improvements and extensions to the method (procedure) that would
benefit the scientific investigation.
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