-
Dissolve 1
tablespoon of salt in 1 cup of water.
-
Mix 1 tablespoon
of liquid dishwashing soap with 3 tablespoons of water in a
small bowl.
-
Swish 1 teaspoon
of plain water around in your mouth vigorously for at least
30 seconds then spit it out in a small cup.
-
Put 1/4 teaspoon
of the salt water into a test tube or small bottle with a
lid.
-
Pour your spit
water from the cup into the test tube.
-
Add 1/4 teaspoon
of the detergent solution into the test tube.
-
Cover the top
with plastic wrap or a lid.
-
GENTLY turn the
tube or jar almost upside down several times. Avoid
making any bubbles.
-
Take the lid off
and dribble about 1 teaspoon of the rubbing alcohol down the
side of the tube into the mixture. Look for the
alcohol to form a layer above the spit/salt/detergent
mixture.
-
Did a stringy
white layer form? That gunk is made up of your DNA.
Each string is made up of thousands of DNA molecules all
stuck together.
-
The dishwashing
detergent broke the cells down, releasing the DNA into the
mixture. The salt combined with the DNA and the DNA
clumped together where the water and alcohol layers met.
-
You may be able
to hook out the strands of DNA with a glass hook (or one
made from a plastic twist-tie) by slowly dipping up and down
through the two layers. If this doesn't work, gently invert
the tube several times until the alcohol is mixed in. The
precipitated DNA will look like a small ball of white
thread.
