How to Extract DNA From Your Saliva

In our Discover Dentistry Course we introduce you to the basics of saliva but this experiment will demonstrate just how complex this liquid is by revealing the quantity of biological matter that saliva contains.

In this video, Dr Lynne Bingle shows you how you can extract the DNA from your own saliva at home, and explains why DNA samples from your mouth may be more popular in the future.

This experiment uses alcohol, so under 18s must ask permission and assistance from their parent/guardian before attempting the experiment.

Extracting DNA From Your Saliva

Equipment needed:

• A small glass or cup (something transparent is best)
• Salt
• About 5ml of Washing-up liquid (detergent)
• About 10ml Alcohol* – we used cheap vodka but any strong, clear alcohol will work
• About 5ml Saliva (although as much as you can get!)
• A cocktail stick or toothpick – to spool the DNA strands onto

Note: If you do not want to use or buy drinking alcohol, you can also use Isopropyl alcohol (which is sold as a cleaning solvent).

Instructions

1. First you will need to get your saliva. You’ll need as much as you can get, and thinking of food you like will help to stimulate the salivary glands. Remember to rub your tongue around your mouth as you do this in order to agitate and loosen cells from the epithelium (your cheek and gums) in your mouth.
2. Add the washing-up liquid to the saliva (about the same amount as you have saliva). The detergent will break down the cell walls (a process called lysis) and expose the DNA (which is not affected).
3. Now the cells are broken apart, we can add a small amount of salt which acts as a flocculant to make the cells’ contents stick together to make it easier to see. Give it a gentle swirl for 30 seconds or so.
4. Finally we add the alcohol by gently pouring it down the side of the glass. This will allow us to see the DNA by bringing it out of solution. DNA is soluble in water, but not in alcohol. Adding the alcohol will force the DNA out of solution and make it visible. You might need to wait a few minutes for the solution to become clearer and to be able to see your strands of DNA.
5. Use a cocktail stick or toothpick to ‘spool’ the DNA and see the strands more clearly.