Name______________________________________________
Genie in a Bottle: Extracting DNA from Your Cheek Cells
Background: __________________ carries the genetic information in all living
organisms, including humans, other animals, plants, and bacteria. Each cell in your
body has a _________________ with multiple ___________________________. Each
chromosome contains a DNA molecule with multiple ______________________.
1. Prior Knowledge: Draw and label a simple diagram of an animal cell. Label the cell
membrane, nucleus, endoplasmic reticulum.
a. What is the function of the nucleus?
b. Chromatin, found in the nucleus, condenses to form what structures inside the nucleus?
2. Prior knowledge: Draw and label a simple diagram of a chromosome. Label the
chromosome, chromatid, and centromere.
a. Where is DNA located?
b. What are the four nitrogen bases and how are they always paired?
c. What does a group of three DNA bases code for in the genetic code?
PROCEDURE:
Step 1: Detergent
Add a small amount of detergent to a test tube (about 0.25 mL). Now carefully pour the drink containing
your cheek cells into the test tube with detergent until the tube is half full.
Step 2: Enzymes
Add a pinch of enzyme (meat tenderizer) to your test tube. With your thumb (or palm) covering the top
of the test tube; gently invert the tube five times to mix. Let the mixture sit for at least 10 minutes. While
you are waiting, watch the Ted Ed video answer the following questions.
1. What part of the cell contains the entire genome?
2. What is the total length of the human genome?
3. What is each tiny mass of DNA called?
4. How many chromosomes does a human have?
5. For each of the following, indicate whether you think it contains DNA (Y = yes; N = no).
bananas ___ fish ___ glass___ meat ___ metal ___ mushrooms ___ spinach ___
Explain your reasoning…
Step 3: Alcohol
Using a pipette, slowly add cold rubbing alcohol; 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 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.
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, read and answer the following questions
These drawings show
two more short sections
of DNA.
The base-pairing rules
describe which bases pair
together in the DNA
double helix. Complete
the following sentences
to give the base-pairing
rules.
1. A in one strand always
pairs with _____ in the
other strand.
C in one strand always
pairs with _____ in the
other strand.
(http://www.biorad.com/cmc_upload/Literature/12525/4006096G.pdf)
2.
For the two sections of DNA shown above:
Is the arrangement of the sugar and phosphate groups the same in both sections of
DNA?
Do both sections of DNA contain the same four bases (A, C, G, and T)?
Are the base-pairing rules the same in both sections of DNA?
Is the sequence of the nitrogen bases the same in both sections of DNA?
3. What is the only difference between these two sections of DNA?
4. Explain why DNA replication is needed before a cell divides into two daughter cells.
Yes or
No
Step 4: Making Your Necklace
By now your DNA should be visible as clumps of white strands floating in or just at the bottom of the
alcohol layer. There may be air bubbles attached to the strands.
Now you are ready to transfer your DNA from the test tube to your necklace. Transfer the DNA to the
small capped tube and fill it the rest of the way with alcohol. Close the cap of the tube around a piece of
string. Now you have a necklace with your very own DNA!