Extracting DNA from tomato

Procedure

• Put 10 mL of ethanol in the refrigerator/freezer in a plastic tube.
• Blend the tomatoes with the hand mixer, for 10 seconds every 10 seconds (if necessary, water can be added).
• Put 5 mL of the tomato blend into a plastic tube.
• Add 10 mL of the buffer solution prepared in a 250 mL beaker (the recipe for the buffer solution is: 120 mL of water, 5 g of table salt, 10 g of sodium bicarbonate, and a bit of dish soap).
• Gently mix the mixture for 2 or 3 minutes. We should try not to generate too much foam but make sure the components are well mixed.
• Filter the tomato sample.
• Transfer 5 mL of the liquid fraction to another plastic tube and add 10 mL of cold ethanol very slowly, trying to make the ethanol slide down the walls of the tube.
• Observe that two phases form, and just in the area of the interface, we will see a cloudy zone with whitish filaments. This zone contains the DNA, and we can observe it with the naked eye.
• Extract the DNA with tweezers or with a pipette acting as a hook and spread the DNA on filter paper. Take a photo!

Theoretical explanation

All living organisms have genes, and tomatoes are no exception! Regarding the components present in the extraction solution: the soap helps to dissolve the cell membranes, salt is added to break the protein chains that bind the nucleic acids, thus releasing the DNA strands. Additionally, ethanol is used because DNA is insoluble, especially when it is cold, and therefore the DNA precipitates out of the solution.