Nova, an American TV
series, have a great experiment. You can extract your DNA using
ingredients in your kitchen!
What you need:
- 500ml bottled water
- 3 x clear plastic cups or glasses
- Clear washing up liquid
- 1 tbsp table salt
- 100 ml isopropyl alcohol
- Blue food colouring
Ask an adult for help when using isopropyl alcohol. Have a look
at this video to see how Nova do it:
- Mix the bottled water with the salt in a cup. Stir until salt
- Transfer 3 tbsp of the salt water into a separate cup.
- Gargle the salt water for 1 minute. Don't swallow it!
- Spit the water back into the cup.
- Add one drop of washing up liquid to the salt water. Stir
gently. Try not to create any bubbles.
- In a separate cup, mix the isopropyl alcohol and 3 drops food
- Gently pour the alcohol and food colouring mixture into the
salt water cup. Tilt the salt water cup as you pour, so the alcohol
mixture forms a layer on top of the salt water.
- Wait for 2.5 minutes. You should see white clumps and strings
The white clumps and strings are your DNA!
When you gargle the salt water and spit it back out, some of
your cheek cells become suspended in the salt water. The more
vigorously you gargle, the more cheek cells will collect in the
The washing up liquid breaks down your cheek cell membranes.
This causes the DNA to be released into the salt water.
DNA is not soluble in alcohol, so it forms a solid where the
alcohol and salt water layers meet. Most other substances from your
cheek cells stay dissolved in the salt water layer. The white
strings and clumps you see are thousands of DNA molecules clumped
together. Single DNA molecules are far too small to see with the
When you gargle the salt water, you are also collecting some
bacterial cells from the inside of your mouth, so the DNA you see
is a mixture of your DNA and bacterial DNA!