Download DNA Extraction from Human Cheek Cells

Name _______________________
Per. _______
DNA Extraction from Human Cheek Cells
(20 points)
Introduction: DNA molecules of humans are very long and contain about 30,000,000 base pairs in a single
string of DNA. How is so much DNA packed into such a tiny cell nucleus? DNA is wrapped around proteins
called histones. When the DNA is curled around the histones and is tightly packed its name changes to
chromosomes, this means the DNA is ready to be copied. Humans have 46 chromosomes packed into a
single nucleus in each cell. In order to study and understand the structure DNA, it first must be extracted from
the nucleus of a cell intact.
1. What does the word ‘extracted’ mean? ________________________________________
Cells do two things – grow and divide. That’s it! When the cells are growing, the DNA is thin and stringy.
When the cells are dividing, the DNA is coiled up into chromosomes.
2. Predict what your DNA will look like (I know, it is just a total guess!). _______________________________
________________________________________________________________________________________
Materials
Gatorade
3 Bulb Pipettes
20% clear dish soap Solution
7 ml water
4 ml Cold Ethyl Alcohol
Paper Dixie cup
15ml Test Tube with Lid (aluminum foil)
Wooden stir rod (optional - used to spool DNA out of tube)
Procedure:
1. This extraction works best if you have not just recently eaten or chewed gum.
2. Measure 7ml of water and pour it into the paper cup.
3. Take the water and violently swish the water in your mouth, making sure to rub your tongue
along your cheeks for 30 seconds.
4. Carefully spit the water mixture back into the paper cup.
5. Pour the spit-water into a test tube until is about half full (you will not use all of the water).
6. Add 10 drops of the Soap Solution
7. Add 10 drops of the Gatorade
8. Place the aluminum foil on the test tube.
a. Make sure your aluminum foil lid does not come off – keep your thumb on it!
9. Gently rock the tube back and forth for 2 minutes, then put your test tube in a rack.
a. Did I mention do it gently?!!!
10. Leave your tube in the rack, and add 4 ml Cold, Ethyl Alcohol.
a. DO NOT tip or mix the Test Tube or you may not see DNA!
11. If you look to the line of separation between the liquid and alcohol, you will start to see tiny hair
like white strings. These strings are your DNA.
DRAW the DNA that you see.
12. Using a wooden stick, get the DNA out by slowly lifting it until it is completely removed from the
test tube. Look at it… check it out… then throw it away!
Discussion of Results and Conclusion:
1. How many chromosomes do humans have? ______________________
2. How many do we get from mom? ________ Dad? _____
3. In words, describe what the DNA looked like in the tube.
4. Look back at your hypothesis. Now that you have seen DNA, was your prediction correct?
5. Discuss at least two sources of error that you can think of which may have caused your
experiment to be inaccurate.
6. What changes in the experiment could eliminate those errors in future experiments?