Molecules to Cells

Extracting DNA from fruit

Equipment and materials
• Liquidiser
• Vegetable knife and chopping board
• Water bath at 600C
• Ice bucket with ice
• 100 ml measuring cylinder
• 250 ml beaker
• Filter funnel
• Coffee filter
• Stop watch
• Glass rod
• Boiling tube and rack
• Dropping pipette
• Soft fruit such as peach. Nectarine, kiwi
• 250 ml beaker containing 50 ml sodium chloride / detergent solution (green coloured)
• Protease solution
• Ice-cold ethanol

Method

1. Chop the fruit into small pieces and cover with 50cm3 sodium chloride/detergent solution in a beaker.
2. Stir the mixture and then incubate in the 60°C water bath tor 15 minutes.
   From this stage the mixture must be kept ice cold and each stage must be carried out as quickly as possible to get the best results.
3. Cool in the ice bath for 5 minutes.
4. Liquidise the mixture for 5 seconds at high speed.
5. Filter the mixture into the second beaker then transfer to a boiling tube. Do not poke at the filter paper – it will tear. Instead, wait for the liquid to filter through.
6. To extract the DNA, add five drops of protease to the filtered tissue extract in the boiling tube, then mix well.
7. Carefully pour a layer of ice-cold ethanol on top of the mixture. Leave to stand for a few minutes.
8. The precipitated DNA should form a web of tangled fibres, which can be drawn up from the tube by carefully rotating a glass rod at the interface between the two layers - see figure over the page.