Name: _______________________________________
This lab was designed with help from the Genetic Science Learning Center,
University of Utah, http://learn.genetics.utah.edu.
Instructor Notes:
DNA can be extracted from virtually anything. Peas, spinach and chicken liver are the most commonly
used substances. The use of peas creates a natural connection to Gregor Mendel.
This lab can be accomplished in less than an hour.
If more than an hour is available students may also blend and strain the pea mixture.
1 pound of peas creates sufficient pea extract for a class of 25 students.
Remind students to be patient as they wait for the DNA to rise into the alcohol.
The University of Utah Genetics Learning center contains a wide range of helpful information relating to
this lab and genetics in general.
Instructor Preparation:
1. Begin soaking peas approximately ½ hour before class.
2. Add ¼ cup of salt.
3. After peas are softened, blend them in water until they have the consistency of baby food.
4. Strain out the solids in the blended peas using a coffee filter, cheese cloth, or other filtering device.
Step 1: Collect equipment
Each group will need the following:
1 test tube
1 beaker to hold test tube
1 disposable pipette
1 tooth pick
Step 2: Collect approximately 10 ml worth of pea extract in the bottom of your test tube—enough to fill the
bottom 2 inches of your test tube. Amounts can vary.
Step 3: Dissolve the cell membrane
add 1 drop of liquid hand soap to your mixture
Shake slightly by placing hand your hand on top of the test tube and giving it a shake. Please be careful
not to splash the liquid or you will smell like peas for the rest of the day!
Wait 5 minutes for the hand soap to dissolve the cell membrane.
Start time: __________________ End Time: ________________
While you are waiting, you may begin reading and answering the questions on the following pages.
Pea DNA Extraction © John R. Sowash | April 2009 | Permission to redistribute granted
Step 4: Cut the DNA
Use the sink to get your tooth pick wet (don’t lick it!).
Insert the tooth pick into the meat tenderizer. Some should stick to the toothpick.
Allow the pea extract to remove the tenderizer from the toothpick. To do this you will need to tip your
test tube until you can dip the tooth pick into the liquid. Shake slightly. If you shake too hard, you will
destroy the DNA!
Step 5: Add Alcohol (Safety glasses on!)
Using your CLEAN pipette, add an equal part isopropyl alcohol to your solution.
You are attempting to create a layer on top of your pea extract (most of which is water). To do this,
gently squeeze the pipette and allow the alcohol to run down the side of the test tube. Do not mix the
two solutions together!
Step 6: Watch and Wait!
You should now have two clearly distinguishable solutions—the pea extract (which is green and cloudy)
and the alcohol (clear).
After a few minutes, you will begin to see columns of a white “snotty” substance begin to form in the
alcohol (top) layer. This is the extracted DNA!
Pea DNA Extraction © John R. Sowash | April 2009 | Permission to redistribute granted
Blending separated the pea cells. But each cell is surrounded by a sack (the cell membrane). DNA is found
inside a second sack (the nucleus) within each cell.
To see the DNA, we have to break open these
two sacks.
We do this with detergent.
Why detergent? How does detergent work?
Think about why you use soap to wash dishes or
your hands. To remove grease and dirt, right?
Soap molecules and grease molecules are made
of two parts:
Heads,
which like
water.
Tails, which hate water.
Both soap and grease molecules organize
themselves in bubbles (spheres) with their
heads outside to face the water and their
tails inside to hide from the water.
When soap comes close to grease, their similar structures cause them to combine, forming a greasy soapy ball.
Pea DNA Extraction © John R. Sowash | April 2009 | Permission to redistribute granted
In this experiment, meat tenderizer acts as an enzyme to cut proteins just like a pair of scissors.
The DNA in the nucleus of the cell
is molded, folded, and protected
by proteins.
The meat tenderizer cuts the proteins
away from the DNA.
Pea DNA Extraction © John R. Sowash | April 2009 | Permission to redistribute granted
How well do you understand this lab?
1. What is the purpose of adding soap to the pea extract?
Dish soap helps to break down the lipid membrane that surrounds the cell and the nucleus. In order to
extract the DNA, we must first separate the DNA from its protective covering.
2. What is the purpose of adding meat tenderizer to the pea extract?
DNA is neatly coiled around proteins called histones. In order to separate the DNA from the rest of the
cellular material, we must cut away the proteins. The enzymes in meat tenderizer remove the histones.
3. The pea cells in the mixture were lysed (dissolved). What indicates that this process has occurred?
We know that we have dissolved the contents of the cell when we begin to see the cloudy DNA rise up
into the alcohol layer. The lower layer of liquid contains the rest of the contents of the cell.
4. Please sketch your test tube and label the following:
a. Pea extract
b. Isopropyl Alcohol
c. DNA Strands
Student drawings will vary, but generally, the pea extract should be at the bottom
of the test-tube, the alcohol at the top, and the DNA strands suspended between
the pea extract and alcohol.
Additional Questions to Consider:
1. What is an enzyme?
2. Will the number of chromosomes in an organism affect the amount of DNA that is separated?
3. How could this process be useful to a geneticist?
4. Are there differences between the extraction of DNA from plant cells and animal cells?
Pea DNA Extraction © John R. Sowash | April 2009 | Permission to redistribute granted