DNA in different foodstuffs.
In this experiment you will perform a rapid DNA extraction from different types of fruit.
You will need:
- Two transparent glasses, the narrower the better
- A fork
- A knife
- Small plate or saucer
- Washing up liquid – preferably blue or red
- Water
- Surgical spirit
- Food colouring
- Fruit, like banana and kiwi fruit
And last but not least ... a helping hand from an adult.
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Method
First of all you will need to separate out the cells from each other. Peel the fruit so that you can mash it up. Now cut the fruit into small pieces and mash it up using a fork. Take care not to spill any juice and that you mash the fruit well. Use a generous amount of fruit. The more you use, the more DNA you’ll get.
When we wash dishes we use washing up liquid as it attacks fats and removes them from our plates. Cells are made up of DNA and proteins surrounded by a coat of fats. So now add some washing up liquid and stir well so that is starts breaking the cells open. The DNA will then be free and ready for the last part of your experiment.
In the glass we now have loads of broken up cells floating around in washing up liquid and water. Once a lot of cells have been broken open, the contents of these cells are also in this mixture. The DNA is now free in the water. You now need to separate it out of the mixture.
All you have to do to separate out the DNA is to add some surgical spirit. The colder it is the better. Pour some into a clean glass, and add some food colouring. Stir well and then slowly tilt the glass with the mashed up fruit and gently pour the surgical spirit down the side of the glass so that it forms a clear layer on top of the fruit mixture. You should add enough surgical spirit to have a two centimetre layer. When you’re done, GENTLY tilt the glass back to standing.
If you look closely you can see that between the lower fruit mixture layer and the upper coloured surgical spirit layer there is another cloudy layer forming. If you leave it for enough time, it will float over the surgical spirit. This cloudy stuff is DNA. Using a toothpick or hairpin or opened paper clip you can pick some up – it feels a bit like wet cotton wool.