I. Purpose:
The purpose of this activity is become familiar with lab
procedures for extracting DNA, collect a DNA sample
and observe the physical characteristics of DNA.
Safety Precautions:
 Do not eat or drink in the laboratory.
 Wear Apron & Safety Goggles.
Research
 What is the purpose behind DNA?
 What is DNA composed of?
 What do you think DNA will look like?
 Where is the DNA located?
Background:
The long, thick fibers of DNA store the information for
the functioning of the chemistry of life. DNA is present
in every cell of plants and animals. The DNA found in
strawberry cells can be extracted using common,
everyday materials. We will use an extraction buffer
containing salt, to break up protein chains that bind
around the nucleic acids, and dish soap to dissolve the
lipid (fat) part of the strawberry cell wall and nuclear
membrane. This extraction buffer will help provide us
access to the DNA inside the cells.
Materials:
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heavy duty ziploc bag
1 strawberry
10 mL DNA extraction buffer (soapy, salty water)
cheesecloth
funnel
50mL vial / test tube
glass rod, inoculating loop, or popsicle stick
20 mL ethanol
Procedure:
1. Place strawberry in a Ziploc bag.
2. Smash/grind up the strawberry using your fist and
fingers for 2 minutes. Careful not to break the bag!!
Procedure:
3. Add the provided
10mL of extraction
buffer (salt and soap
solution) to the bag.
4. Kneed/mush the
strawberry in the bag
again for 1 minute.
5. Assemble your
filtration apparatus as
shown to the below.
Procedure:
6. Pour the strawberry slurry into the filtration
apparatus and let it drip directly into your test tube.
7. Slowly pour 20 ml of cold ethanol into the tube.
OBSERVE
8. Dip the loop or glass rod into the tube where the
strawberry extract and ethanol layers come into
contact with each other. OBSERVE
9. Swirl the glass rod around to grab the DNA at the top
of the ethanol and place inside the vial. Remove all
the DNA that is in the tube.
Conclusion, Data and Analysis:
DNA Extraction Table
Amount Added
or Obtained
Initial Color
Purpose
Buffer (soap-salt
mixture)
Strawberry
Cold Alcohol
DNA
Sketch of test tube with contents:
Conclusion and Analysis:
1. It is important that you understand the steps in the
extraction procedure and why each step was
necessary. Each step in the procedure aided in
isolating the DNA from other cellular materials.
Match the procedure with its function:
Procedure:
A. Filter strawberry slurry
through cheesecloth
B. Mush strawberry with
salty/soapy solution
C. Initial smashing and
grinding of strawberry
D. Addition of ethanol to
filtered extract
Function:
___ To precipitate DNA
from solution
___ Separate components
of the cell
___ Break open the cells
___ Break up proteins and
dissolve cell membranes
2. What did the DNA look like? Relate what you know
about the chemical structure of DNA to what you
observed today.
3. Explain what happened in the final step when you
added ethanol to your strawberry extract.
(Hint: DNA is soluble in water, but not in ethanol)
4. 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 our DNA
extraction? Explain.
5. Why is it important for scientists to be able to remove
DNA from an organism? List two reasons.
6. Is there DNA in your food? ________ How do you
know?
I. Purpose:
The purpose of this activity is to understand all
organisms are made of the same material. The only
difference is that the genetic material is simply
rearranged.
Safety Precautions:
 Do not eat or drink in the laboratory.
Background:
Cells from the lining of your mouth come loose easily, so you will
be able to collect cells containing your DNA by swishing a liquid
around in your mouth.
The cells from the lining of your mouth also come off whenever you
chew food. How do you think your body replaces the cells that
come off the lining of your mouth when you eat?
To extract DNA from your cells, you will need to separate the DNA
from the other types of biological molecules in your cells.
You will be using the same basic steps that biologists use when they
extract DNA (e.g. to clone DNA or to make a DNA fingerprint).
You will follow these 3 easy steps to extract the DNA:
Detergent
eNzymes (meat tenderizer)
Alcohol
Materials:
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Sports Drink / Water
DNA extraction buffer (soapy, salty water)
Water bath @ 50 degrees C
50mL vial / test tube
glass rod, inoculating loop, or popsicle stick
Protease enzyme (meat tenderizer)
ethanol
Procedure:
1. Obtain 3ml of sports drink or water
2. Begin chewing on the inside of your mouth (Do not
cause bleeding)
3. Place sports drink / water in mouth & swish
vigorously for 30 seconds
Procedure:
4. Spit back into tube.
5. Add 2ml of buffer to tube (record observations)
6. Invert 5 times (do not shake)
7. Add a small pinch of enzymes (meat tenderizer)
8. Invert 5 times (do not shake)
9. Add 5ml of ethanol to tube by leaning the tube at a
45º angle and dropping ethanol down the side.
10. Place cap on tube and allow it to sit undisturbed for
5 minutes.
11. Slowly invert tube 5 times to help the DNA which as
begun to precipitate to aggregate.
Procedure:
12. Use wooden stick to obtain DNA and place inside small
vial.
Observations, Analysis, Data:
1. Which of the following do you think will contain DNA?
Explain your reasoning.
bananas __
concrete __ fossils __ meat __ metal
__ spinach __ strawberries __
2. Describe the function of DNA polymerase. Explain why
each part of the name DNA polymerase (DNA, polymer,
-ase) makes sense.
3. The detergent and meat tenderizer opened the cell and
broke down the cell components so that the DNA could
be obtained. What other components of the cell might
be found in the sample in your capped tube?