Download Dining On Delicious DNA Handout

Name________________________
Date____________
Dining on Delicious DNA: Strawberries
Purpose: For this lab you will observe DNA in the food you eat.
Background:
Strawberries! You find them in all your favorite desserts: ice cream, cake,
chewing gum, preserves, etc. Many like to eat them fresh though allergic responses to
their consumption have been documented. But did you know that it is very easy to
extract and observe the DNA of strawberries?
Deoxyribonucleic acid (DNA) forms long thick fibers and stores the information for
processing the chemistry of life. DNA is present in every cell of plants and animals.
Strawberries happen to have large genomes; they are octoploid, meaning they have
eight of each type of chromosome in each cell. Because of this, we are able to extract
and observe strawberry DNA very easily using everyday household materials.
Before you start:
What do you think the DNA will look like?
Where is DNA found?
Materials:
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heavy duty Ziploc bag
1 strawberry
30 mL water
10 mL detergent
50 mL beaker
1mL salt
cheesecloth
funnel
50mL vial/test tube
wooden skewer, glass rod, inoculating loop, or toothpick
20mL ethanol (denatured alcohol) or 70% rubbing alcohol (chilled)
DNA extraction buffer preparation:
What is the buffer and how does it work?
1. Mix 30 mL water and 10 mL detergent in a 50mL beaker.
2. Add a pinch of salt (1mL).
3. Stir.
DNA extraction procedure:
1. Place strawberry in Ziploc bag.
2. Crush strawberry inside bottom of bag by pressing on it with your fingers.
3. Add 10mL of the extraction buffer you made at the beginning.
4. Continue pressing the strawberry, mixing it with the buffer solution.
5. Assemble a filtration device over an empty test tube. Cut cheesecloth to fit over the
mouth of the funnel and insert funnel into the beaker.
6. Pour the strawberry slurry into the filtration apparatus and let it drip into the beaker.
Do not force the slurry into the cloth as this rips DNA.
7. After a few minutes, remove the funnel and add cold ethanol.
8. Observe.
9. Use a meat skewer to pick up the white fibrous strands of material. This is DNA.
Observe.
Analysis:
1. Match each procedure used in this lab to its role in the DNA extraction process:
Procedure
Role Played
A. Smashing and grinding of strawberry.
___ separate cell components
B. Mix strawberry slurry with buffer
solution.
___ break open cells
C. Adding ethanol to slurry extract.
___ precipitate DNA from solution
D. Filter strawberry slurry through
cheesecloth.
___ break up proteins/membranes
2. Is there DNA in food? _________ Explain:
3. Draw the extraction buffer as it might look as it acts on the cell:
4. Draw the DNA as it appeared in your vial:
5. Describe the appearance of the DNA in your own words. Use descriptors such as
color, shape, length, strength, behavior, smell, etc.
6. DNA strands can be EXTREMELY long, but they fit into the nucleus of a single cell.
How does the structure of DNA enable it to carry dense information in a tiny space?