Name_____________________________
Block________________
Date_______
DNA Extraction Lab
Background information: DNA, or deoxyribonucleic acid, is the hereditary material in humans and
almost all other organisms, including plants, fungi, animals, and bacteria. DNA contains the biological
instructions that make each species unique. DNA, along with the instructions it contains, is passed from adult
organisms to their offspring during reproduction. Nearly every cell in a person’s body has the same DNA. Most
DNA is located in the cell nucleus (where it is called nuclear DNA) surrounded by a wall, called a nuclear
envelope. The nucleus sits in the middle of a cell. The whole cell is surrounded by a plasma membrane, which
serves as a barrier keeping the cell’s contents inside protected from the outside environment). The cell itself is
surrounded by a plasma membrane composed of lipids. A lipid is a macromolecule mainly composed of
carbons and hydrogens. It is a nonpolar molecule that includes oils, steroids, and waxes. Lipids are insoluble
in water because water is polar. Lipids are soluble in Detergents and soaps because these are nonpolar. The
latter are used in DNA extraction for the purpose of taking up the lipid plasma membrane, which is a barrier to
the DNA.
Because the cell is very small, and because organisms have many DNA molecules per cell, each DNA molecule
must be tightly packaged and wrapped around proteins called histones. This packaged form of the DNA is
called a chromosome. During DNA extraction, the proteins must be removed the DNA in order to loosen form
of the DNA. Enzymes are used during the process to cut those histones apart. DNA isn’t always tightly packed
into chromosomes. During cell division, DNA unwinds so it can be copied and the copies transferred to new
cells. DNA also unwinds so that its instructions can be used to make proteins and for other biological
processes. DNA is a long, stringy molecule. DNA normally stays dissolved in water, but you will add salt in step
one to help those molecules stick together. When salty DNA comes in contact with alcohol it becomes
undissolved. This is called precipitation. The physical force of the DNA clumping together as it precipitates
pulls more strands along with it as it rises into the alcohol. You can use a wooden stick or a straw to collect
the DNA. If you want to save your DNA, you can transfer it to a small container filled with alcohol.
GOAL: In this lab, you and your partners will isolate DNA using common household items! You will ascertain if
there is a difference between using hand soap or dish detergent during the DNA extraction process. To keep
the strands of DNA intact throughout the isolation, you need to handle everything gently. If you do this, you
will be rewarded at the end with long, gooey strings of DNA.
After reading the background information and goal, write a question for this experiment and a
hypothesis:
Question:_____________________________________________________________________
_____________________________________________________________________________
Hypothesis:___________________________________________________________________
_____________________________________________________________________________
Name_____________________________
Block________________
Date_______
Materials:
 Spinach
 Enzymes (Meat tenderizer)
 Graduated cylinder
 4 Test tubes
 Mortar and pestle
Procedures:





Detergent
Salt
Water
Filter paper
2 small beakers
 Rubbing alcohol (70-90%
isopropyl or ethyl alcohol)
 Stirring rod
 Gloves
Step 1: Make sure you have gloves on and goggles. Safety first! Label your beakers and test
tubes. 2 test tubes and 1 beaker should be labeled D = Detergent and the others should be
labeled H = Hand Soap. Give each test tube a number 1-2 as well. See results table below.
Step 2: Grind the spinach using a mortar and pestle until like paste. This will separate the
spinach cells.
Step 3: Add 100ml of cold water and a pinch of salt (less than 1ml). Stir thoroughly. The salt
will keep those DNA molecules together.
Step 4: Pour your thin spinach cell soup into two small beakers. Use the filter paper to keep
the chunks out of your beaker. Each beaker should have half of your mixture. Squeeze the
filter paper to get as much of the spinach mixture as possible.
Step 5: Add 15ml of liquid detergent to one beaker and swirl to mix. Let the mixture sit for 510 mins.
Step 6: Repeat step 6 with your second beaker using 15ml of hand soap.
Step 7: Pour the mixtures into the appropriate test tubes, each about 1/3 full. The detergent
will brake apart the cells’ membranes and the membrane of their nuclei.
Step 8: Add a pinch of enzymes (about 1 ml) to each test tube and stir gently. Be careful! If you
stir too hard, you'll break up the DNA, making it harder to see. DNA is tightly wrapped around
proteins called histones. The enzymes are used to cut the histones apart to loosen DNA.
Step 9: For each test tube, tilt your test tube and slowly pour rubbing alcohol (70-95%
isopropyl or ethyl alcohol) into the tube down the side so that it forms a layer on top of the
spinach mixture. Pour until you have about the same amount of alcohol in the tube as spinach
mixture. Alcohol is less dense than water, so it floats on top. Look for clumps of white stringy
stuff where the water and alcohol layers meet.
Step 10: Very gently swirl the stirring in the alcohol to wrap the DNA around the rod.
Name_____________________________
Block________________
Date_______
Step 11: Examine the amounts of DNA you extracted. Record your observation for each test
tube.
You Have Just Completed DNA Extraction! Now clean up!
Now that you've successfully extracted DNA from one source, you're ready to experiment
further. Science Fair possibilities:
Experiment with other DNA sources. Which source gives you the most DNA? How can you
compare them?
Experiment with different soaps and detergents. Do powdered soaps work as well as liquid
detergents? How about shampoo or body scrub?
Experiment with leaving out or changing steps. We've told you that you need each step, but is
this true? Find out for yourself. Try leaving out a step or changing how much of each
ingredient you use.
Do only living organisms contain DNA? Try extracting DNA from things that you think might
not have DNA.
Results:
Observations
Table
DNA in
Test tube 1
DNA in
Test tube 2
(Observe quantity)
(Observe quantity)
Dish Detergent
Hand Soap
Questions:
1. What does DNA look like?
Further Observations
(anything of note during
experiment)
Name_____________________________
Block________________
Date_______
2. Why is it important for scientists to be able to remove DNA from cells?
3. Explain the role of detergent, ethanol, and salt in the extraction process?
4. Is there DNA in your food? How do you know?
5. If DNA is so small it fits in one cell, how are we able to see it with our eyes after extraction?
6. Why are you not harmed (or altered) by ingesting the DNA of another organism? What
implication does this have for farmers who would use GM (genetically modified) plants?
7. No experiment is perfect. What could you have done differently to improve the outcome of
your experiment?