Name: ___________________ Date: _______ Period: ________
DNA Extraction Lab
Lab Biology and Forensics
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 wheat germ 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 cell wall and nuclear
membrane. The extraction buffer will help provide us access to the DNA inside the cells.
Wheat Germ- What is it?
Walk past any health food store and you will no
doubt see advertisements for wheat germ. Wheat
germ is one of the most nutritional products
available. In fact, wheat germ contains 23 nutrients,
and has more nutrients per ounce than any other
vegetable or grain.
Wheat germ is a part of the wheat kernel. The germ
is only a very small part of the kernel, approximately
2 ½ percent in total. The word germ does not have
anything to do with bacteria; it simply refers to
germination. The germ is the reproductive part that
germinates and forms the wheat grass.
Objectives:
 To observe the physical and chemical properties
of DNA
 To understand one process of DNA extraction
 To demonstrate proficiency with one technique
of DNA extraction
Materials:
Wheat germ is very high in protein. It contains
around 28 percent protein and has more protein than
can be found in most meat products. The human
body needs protein in order to repair tissue damage
and to help minerals and nutrients reach our cells.
The amount of nutrients that are contained within
wheat germ seems endless. It contains more
potassium and iron than any other food source. Also
found in great quantities are riboflavin, calcium,
zinc magnesium and vitamins A, B1 and B3.
Vitamins B1 and 3 are very important to maintain
energy levels and maintain healthy muscles, organs,
hair and skin.
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Raw wheat germ
Liquid detergent (Ivory or Woollite)
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95% Ethyl Alcohol
50-60° Celsius tap water
50 ml test tube
Graduated cylinder- measuring spoons, or other measuring devices.
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Glass stirring rod- for stirring and collecting the mixture.
Eyedropper- may be needed to remove foam
Paper towels
Hypothesis: Please make your own hypothesis for this lab.
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Pre-lab Questions:
1. Why do you think wheat germ was chosen for this DNA extraction?
2. Give 3 examples of other substances DNA can be extracted from.
3. What do you think the extracted DNA will look like?
4. In what part of the cell is DNA found?
5. Why is it important for you to know the structure of DNA?
6. What are the 4 nucleotide bases in DNA?
7. Why do you think we are extracting DNA from 2 different sources?
8. Why do you think the procedures call for the use of cheesecloth/coffee filter and
a funnel?
9. What is the reason for using salt in the DNA extraction buffer?
10. What is the reason for using detergent/dish soap to the DNA mixture?
Procedures:
1. Place 1 gram or 1 teaspoon of raw wheat germ in a 50 ml test tube, beaker or jar.
2. Add 20 ml or 1 tablespoon of hot (50-60 °C) tap water and mix constantly for 3
minutes.
3. Add 1 ml or a scant 1/4 teaspoon of detergent and mix gently every minute for 5
minutes. Try not to create foam.
4. Use an eyedropper, pipette, or piece of paper towel to remove any foam from the
top of the solution.
5. Tilt the test tube, beaker or jar at an angle. SLOWLY pour 14 ml or 1 tablespoon
of alcohol down the side so that it forms a layer on top of the water/wheat
germ/detergent solution. Do not mix the two layers together. DNA precipitates at
the water-alcohol interface (the boundary between the water and the alcohol).
Therefore, it is crucial to pour the alcohol very slowly so that it forms a layer on
top of the water solution. If the alcohol mixes with the water, it will become too
dilute and the DNA will not precipitate.
6. Let the test tube, beaker or jar sit for a few minutes. White, stringy, filmy DNA will
begin to appear where the water and alcohol meet. You will usually see DNA
precipitating from the solution at the water-alcohol interface as soon as you pour
in the alcohol. If you let the preparation sit for 15 minutes or so, the DNA will float
to the top of the alcohol.
You can usually get more DNA to precipitate from the solution by using one of
the DNA-collecting tools (such as a glass or paper clip hook) to gently lift the
water solution up into the alcohol. This allows more DNA to come in contact with
the alcohol and precipitate. You may find it helpful to pour the water/detergent
solution into a clean test tube, leaving behind the wheat germ, before adding the
alcohol.
7. Use a glass or paper clip hook or a wooden stick to collect the DNA.
8. If you want to keep the DNA, store it in 50 - 70% alcohol in a sealed tube or airdry it on paper towels or filter paper.
9. Make a wet mount slide of the DNA, stain with Methylene blue and place it under
a microscope and complete the lab activity handout.
*Caution: methylene blue will stain your skin and clothes so be very careful
when handling it.
Data:
A. Draw a picture of DNA with the left side bases equal to the
AACTTGAGTACC
(label all parts correctly)
following genetic code:
B. Make a drawing of your Extracted DNA
(Visual with naked eye)
C. Prepare a wet mount/stained slide of a small portion of your extracted DNA. Draw your
observations (use medium or high power)
Magnification _________
Questions:
1. List the nitrogen bases found in DNA.
2. What are the base pairing rules?
Observations of DNA
3. Which nitrogen bases are pyrimidines?
5. How many chromosomes do humans have?
4. Which nitrogen bases are purines?
6. How is RNA different then DNA?
Conclusion: Form a conclusion remembering to address your hypothesis.
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