Name_________________________________________________________
Partner(s) Name(s): _____________________________________________
Date________________
Forensic Science
DNA Extraction using DN&A- Detergent, eNzymes, & Alcohol Lab
PROBLEM: HOW DO YOU EXTRACT DNA FROM SOME OF YOUR OWN
CELLS?
PRE- LAB DISCUSSION QUESTIONS:
Read the entire investigation. Then, work with a partner to answer the following
questions in full sentences. Go to https://www.genome.gov/25520880 for help in
answering these questions.
1) Why is DNA so important in forensic science? What is the function of DNA in your
cells?
2) Draw a simple diagram of a cell showing the cell membrane and the DNA in
chromosomes surrounded by a nuclear envelope.
Name_________________________________________________________
Partner(s) Name(s): _____________________________________________
Date________________
BACKGROUND:
Cells from the lining of your mouth come loose easily, so you will be able to collect cells
containing your DNA by swishing liquid around in your mouth.
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 three easy steps to extract DNA: Detergent, eNzymes, Alcohol
MATERIALS:
Sports drink Gatorade (10 mL)
Glove
Liquid dish soap (0.25 mL)
Meat Tenderizer (a pinch)
70-95% isopropyl or ethyl alcohol (4 mL)
Paper cup
Tub of ice
Small test tube (hold a minimum of 15 mL)
Test tube rack
PROCEDURE:
1) Get a small paper cup of Gatorade and a toothpick. Swish the drink in your mouth
vigorously for at least minute in order to obtain enough cheek cells. Slightly running your
teeth over your inside cheeks while swishing is helpful. Think fishy face. Spit the drink
back into the cup. Set aside.
2) Put a glove on the hand you will use to hold your test tube, not the hand you will use to
pour. Obtain a test tube from the test tube rack.
3) Put about 4-5 drops of detergent to the test tube (about 0.25 mL). Now carefully pour
the drink containing your cheek cells into the test tube until the tube is half full—do
NOT put all of the contents into the test tube from the cup.
4) Add a pinch of enzyme (meat tenderizer) to your test tube. With your gloved thumb
(or palm) covering the top of the test tube; gently (you don’t want any bubbles/suds)
invert the tube five times to mix. Remove your glove and throw it into the garbage. Let
the mixture sit for at least 10 minutes. While you’re waiting, answer the questions at the
end of the lab. Refer to the DNA Extraction Virtual Lab worksheet you completed the
last class.
5) Using a pipette, slowly add cold alcohol into the test tube; let the alcohol run down
the side of the test tube so it forms a layer on top of the soapy liquid. Add alcohol until
you have about 2 cm (~ 1 inch) of alcohol in the tube. Alcohol is less dense than water,
so it floats on top. Do not mix or bump the test tube for 10 minutes.
Name_________________________________________________________
Partner(s) Name(s): _____________________________________________
Date________________
DNA molecules will clump together where the soapy water below meets the cold alcohol
above, and you will be able to see these clumps of DNA as white strands. While you are
waiting for the DNA to become visible, answer more of the questions.
6) After about 10 minutes, your DNA should be visible as clumps of white strands
floating in the alcohol layer. There may be air bubbles attached to the strands. Show your
DNA to your teacher.
Teacher signature: ______________________________________________________
QUESTIONS: Go to http://learn.genetics.utah.edu/content/labs/extraction/howto/ for
help in answering these questions!
1) Why did you add detergent to your cheek-Gatorade sample?
2) What do the enzymes do?
3) What is the purpose of adding the alcohol as the final step in DNA extraction?
4) The three components of each nucleotide within DNA are
___________________________________________
___________________________________________
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Name_________________________________________________________
Partner(s) Name(s): _____________________________________________
Date________________
5) The complete name for DNA is ________________________________________.
6) Complete the following sentences to describe the structure of DNA:
In the backbone of each strand in the DNA double helix molecule, the sugar of one
nucleotide is bonded to the __________________________ in the next nucleotide.
The __________________________ of the nucleotides in each strand of DNA extend
toward each other in the center of the DNA double helix molecule.
A in one strand always pairs with ______ in the other strand, and G in one strand always
pairs with _______ in the other strand. These are the base-pairing rules.
7) Which cells in your body contain DNA? Which cells do NOT contain DNA?
8) Why do these cells need DNA?
9) Check off which of the following you think contain DNA:
Bananas______ concrete ______fossils______ meat ______ spinach ______
strawberries______
Explain your reasoning.
10) After a DNA sample is extracted from a person, what would come next in the
forensic science investigation?