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Things to do online and at home.

A selection of online and hands on activities that relate to the science behind this project. No special equipment required.

Extract tomato DNA

You will need
  • 2 Tomatoes
  • ½ Cup of cold water (50 ml)
  • A blender
  • Test tubes or other small glass containers
  • 2 Jugs
  • Rubbing alcohol/surgical spirit thoroughly chilled (available from Boots)
  • Coffee filter paper (or a very fine sieve)
Directions
  1. Make sure the water is thoroughly chilled by leaving in the fridge.
  2. Take the tomatoes and blend at a high speed with the water.
  3. Support a coffee filter above another jug and strain the liquid from the blender into the jug. This gets rid of large particles that might obscure the DNA.
  4. Add a couple of table spoons of washing up liquid and swirl the jug to mix.
  5. Leave to stand for 5-10 minutes.
  6. Pour the mixture out into text tubes or other small glass containers. Fill each one about a 1/3 full.
  7. Very gently pour the chilled alcohol down the side of the container so that it forms a layer on top of the tomato juice. Add approximately the same amount of alcohol as tomato juice to each container.
  8. Leave for 5 minutes – the DNA from the tomato should now be collecting in a layer between the juice and the alcohol.
  9. Insert a cocktail stick into the junction between the alcohol and the tomato juice. Now pull it out there should be a thin whitish thread handing from the stick. This is the tomato’s DNA. If you do it slowly you can wind a whole load of DNA on to the stick as it will keep collecting where the juice and alcohol meet.
  10. If you can’t hook the DNA up with your cocktail stick try swizzling the stick and seeing if the DNA will collect around it.
What's going on?

Blending the tomatoes separates the tomato cells from one another. You then filter the mixture to get rid of the larger unseparated lumps of cells and structural material that might obscure the DNA you extract.

Adding detergent to the tomato soup breaks the membrane surrounding each cell and releases the tomato’s DNA.

The salt you added earlier then helps the DNA precipitate out from solution. The DNA is attracted to the alcohol layer above the tomato juice solution and collects there where individual strands of DNA will come in contact and bind together.

More

Try this same technique with different fruits or vegetables and see what else you can extract DNA from.

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