How to Extract DNA From Fruit and Vegetables
A Home Experiment for Viewing Real Deoxyribonucleic Acid
Nov 9, 2008
Children interested in this experiment should be guided by an adult, especially if using a knife or blender. This experiment also calls for rubbing alcohol. It is important to read the alcohol’s instructions – this is particularly relevant to those wishing to touch the DNA, as some types of alcohol can irritate the skin.
Ingredients and Utensils for Extracting DNA From Fruit and Veg
The following is required for this simple experiment:
- ¼ (one-quarter) cup of rubbing alcohol
- 2 clear glasses
- A container of iced water (suitable for chilling one of the glasses)
- Just under ½ (one-half) cup of tap or distilled water
- A measuring cup
- 2 large pinches of salt (table salt will do)
- 2 tblsps of clear detergent, such as liquid soap or shampoo or dish washing detergent
- A spoon for stirring
- A fruit or vegetable (onions, split green peas, bananas, strawberries and kiwi fruits all work well)
- A sealable plastic bag
- Knife or blender for chopping and mashing (some fruit/veg can be mashed without these)
- A paper coffee filter
- A rubber band
- A glass rod, toothpick or popsicle stick
Method of Extracting DNA From Fruit and Veg
The cup measurements referred to are standard cups.
- Step 1 – Pour the alcohol into one of the glasses. Place the glass into the bowl of iced water to chill, then set aside.
- Step 2 – Pour the tap/distilled water into the measuring cup with the salt. Add the detergent and mix carefully until the salt is dissolved. This is the extraction solution.
- Step 3 – Remove the skins and stems from the chosen fruit/veg. Crush the fruit, either by mashing by hand in the sealed bag, or in a blender. When pulverised, add some of the extraction solution – about 5 teaspoons for a small banana. The consistency should be similar to a thick fruit smoothie.
- Step 4 – Stir the resulting bag (or blender) mixture for 30-60 seconds. Place the filter over the remaining glass, and secure it with the rubber band. Pour the mixture into the filter. If the mixture is too thick, stir in more of the solution. Leave to filter for about 10 minutes.
- Step 5 – Some liquid should have filtered through (the filtrate). Remove the glass of alcohol from the iced water. Pour the filtrate into the alcohol. After about 5 minutes, a clumpy white precipitate – the DNA – should be visible in the alcohol. For a closer look, use the glass rod, popsicle stick or toothpick to hook it up.
- Step 6 – Pour the liquids down the sink and clean the rest of the equipment.
How Does This DNA Extraction Experiment Work?
- The mashing breaks the cells apart. The detergent breaks them open, freeing the cell contents (including the DNA).
- The filtering removes most of the unwanted larger particles.
- The salt has positively charged ions, which stop the negatively charged DNA molecules from repelling each other.
- DNA is soluble in water but not alcohol, therefore the alcohol allows it to precipitate.
To find out more about cells, read Basic Cell Biology for Understanding Genetics. A similar experiment that includes information on how to obtain a more pure DNA extract can be found at the Medical Research Council’s website.
Sources
Extracting DNA from Bananas, PBS (Nova Teachers Activities) website, accessed: 8th November 2006, no author specified.
Fruit Loops, The Biotechnology Institute website, accessed: 9th November 2008, no author specified.
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