Group Members Names: _________________________________________ Date _________ Class Block _______
_________________ _______________________
DNA Extraction Lab
Today you will be extracting your own DNA!! This lab will help you learn more about the structure of DNA. You will
only turn in one copy of the lab per group, but everyone in the group will write on their own lab.
sssPlease make sure you are answering all questions in complete sentencessss
Pre-Lab Questions
1. Where have you heard about DNA before and what do you know about it? Think about the news, talk shows,
things you’ve read, etc.
2. What is the function of DNA?
3. Where is DNA found in our bodies? Explain in words, and then draw a picture to show it in your cells in the
form of chromosomes (you might want to use your mitosis coloring from pg 57 for help).
Extracting DNA from Your Cells
Cells from the inside of your cheek come off easily. They even come off when you eat! For our lab, you will you will
be able to collect a sample of your cells by swishing a liquid around in your mouth.
4. How does the body replace cells that come off from inside your cheeks when you eat? What is this process
called?
5. To extract DNA from your cells, you have to separate the DNA from the other biomolecules in your cells. What
are the biomolecules in your cells, and what are their functions for your cell?
6. What are your cell membranes primarily composed of?
In order to isolate your DNA, you will use these 3 basic materials: Detergent → eNzymes → Alcohol.
This is the same basic process used in forensics and labs to isolate DNA. In order to get the DNA out of your cells,
you must break open the cell membranes and the nuclear membranes, which consist primarily of lipids. As you
know, when you get butter (a lipid) on your hand, you must wash with soap in order to get the butter off because
soaps are able to break up lipids, while water alone cannot do that. The enzyme used in this lab is meat tenderizer.
Meat tenderizer has proteases, which are enzymes that break apart protein. If you stretched out the DNA in one of
your cells, it would be 2-3 meters long. In order for all this genetic information to fit in your cells, it is wrapped
tightly and twisted around proteins called histones. The alcohol is used to cause the free and untwisted DNA to
clump up and come out of the solution, forming a precipitate. The cold alcohol reduces the DNA’s solubility in the
soap solution, which causes the DNA to rise into the alcohol layer. The lipids and proteins stay in the solution.
7. What does the detergent do to your cells?
8. What does the meat tenderizer do to your DNA?
9. How is the DNA able to come out of the soapy solution?
kkk Read through all the steps of the procedure. Underline/highlight key words.kkk
o8oGet a stamp from Mrs. Stevens. o8o
Once you have your stamp, you may begin to gather
materials and complete the procedure.
MATERIALS


Things to bring to your desk: Cup with Gatorade, Test Tube, Beaker, your phone for a timer only (using your
phone for anything else will result in points detucted from your lab)
Community Materials located by the sinks on the counters: Dish Soap, Meat Tenderizer
PROCEDURE
Getting Your Cell Sample
 Rinse your mouth out at a sink if you just ate breakfast/lunch. You need a clean, food-free mouth to get a
good sample of cells.
 Obtain a cup with Gatorade.
 Pour the Gatorade into your mouth and swish vigorously for at least 90 seconds. You must do this step so
you can get the thousands of cheek cells off your cheek and into the Gatorade.
 Spit the drink back into the cup.
Detergent
 Add 2-3 drops of detergent (dish soap) to your test tube.
 Carefully pour your cheek cell solution into the test tube until it is halfway full.
Enzymes
 Add a pinch of enzymes (meat tenderizer) to your test tube.
 Place your thumb over the opening of the test tube and gently invert the tube 5 times to mix.
 Put the test tube gently in your beaker. Let your test tube sit for at least 10 minutes.
 Wash your hands.
 Describe what you see and sketch your test tube in the data table on the next page.
k While you are waiting, work on questions from the DNA Information Page k
Alcohol
 You will need 1 mL rubbing alcohol. Squeeze the bulb of your pipette when it is not in the solution, place
the tip in the alcohol, and then release the bulb. That will be 1 mL.
 Using a pipette, slowly add cold rubbing alcohol into the test tube by letting the alcohol run down the side
of the test tube. You want it to form a layer on top of the soapy solution.
 Describe what you see and sketch your test tube in the data table on the next page.
kk If you add the alcohol too quickly, you may not be able to see your DNA  kk
 DO NOT MIX OR BUMP the test tube for 10 minutes.
k While you are waiting, work on questions from the DNA Information Page. k
 After 10 minutes, check your test tube. Describe what you see and sketch your test tube in the data table
on the next page. You may try to pull the DNA out of the solution by carefully using a pipette.
DNA Extraction Lab Data Table
Sketch
After Adding Enzyme
After Adding Alcohol
After Adding Alcohol,
10 min.
Observations
DNA Extraction Lab: DNA Information Page
DNA consists of two strands of
nucleotides wound together in a
spiral called a double helix. Each
nucleotide contains a phosphate, a
sugar (deoxyribose), and a
nitrogenous base (A, T, C, G)
10.
Based on the figure to the
left, what do you think antiparallel
means?
11. The diagrams below show a small section of DNA from three different organisms. A plant, a mammal, and a
bacteria.
Sunflower
Rabbit
E. coli
12. What does the P represent?
13. What does the S represent?
14. What does the A, T, C, and G represent?
15. The outside sides of the DNA are called the backbone. What two molecules make up the backbone?
16. Compare the DNA backbones for all three organisms. What differences, if any, do you see?
17. Compare the DNA bases for all three organisms. What differences, if any, do you see?
18. Compare the order of the DNA bases for all three organisms. What differences, if any, do you see?
19. Compare the base pairs (A bonds to…?) for all three organisms. What differences, if any, do you see?
20. Based on your answers for 16-19, what can you conclude about the structure of DNA in all organisms?
21. If DNA contains all the genetic information for an organism, what do you think is the reason a sunflower looks
different than a rabbit?
DNA Replication
22. When does DNA replication occur during the cell cycle?
The picture below shows the 3 basic steps for DNA replication. DNA helicase separates the two strands of DNA.
The point of separation is called the replication fork. Then DNA polymerase moves along the strands of the
separated DNA molecule and adds the complementary base pair. During this process, DNA polymerase
“proofreads” the new DNA it’s making and will remove a wrong base if it finds an error.
23. Based on the names of the two molecules involved in DNA replication (DNA helicase, DNA polymerase), what
kind of molecules are these and how do you know? What biomolecule are they? If you don’t know, check your
biomolecule notes on pg. 17-19.
24. The diagram below shows a small segment of the sunflower DNA (from page 1) that has been separated by
DNA helicase. Your job is to play the role of DNA polymerase and create the new matching strands of DNA to
make two pieces of double-stranded DNA in the drawing below. Use the base-pairing rules to determine which
nucleotides to add.
Strand 1
Strand 2
25. Are there any differences between Strand 1 and Strand 2? Are these two molecules of DNA any different from
the sunflower DNA molecule on page 1? What does this tell you about DNA replication?