|This activity is designed to
give students a hands on approach to working with DNA.
In this experiment students will extract DNA from their own
Non Iodized Salt
1 test tube with a cap per person
Chilled ethanol (or isopropyl
Access the Student Journal
for Activity 5
1 Dixie cup per
1 paper clip
5 - Isolate Your DNA
Coding and Translation, you learned about DNA, genes, and coding
proteins. Our DNA is made up of thousands of base pairs
attached to sugars that are wound in an alpha helix form.
Each base pair is so small, that even an electron microscope
cannot see individual base pairs. However, using a
technique to remove DNA from the nuclei in your cheek cells, you
can see clumps of DNA with the naked eye.
1. Make a .9% salt solution with
water (9g/L). Give each student 10mL of the salt solution in a
2. Make a 25% dish washing
detergent solution with
water. Pour 5mL of the soap solution in each test tube.
3. Swish the salt solution in your
mouth for 30 seconds. If you can last longer, swish up to
4. Spit the salt solution back into the
Dixie cup and pour the solution into the test tube until the
tube is 3/4 full.
5. Cap the test tube and VERY GENTLY
(don't shake, because that will create bubbles and break up DNA
rock the tube for 2-3 minutes.
6. Then, tilting the test tube, pour
chilled ethanol along the side of the test tube so that it forms
a layer above the mixture. Pour slowly so you do not mix
the two layers.
7. Let the solution stand for 1-2
8. Straighten the paper
clip, dip it into the test tube, and turn the clip in one
direction near the junction between the ethanol and soapy water. Then slowly
pull the clip through the ethanol solution. You should see
long opaque strands of DNA following the clip. Some air
bubbles may be attached to these strands. Look with a hand
magnifier if you have trouble seeing the strands.