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Learn how to extract DNA at home
You have already heard about DNA, right? The DNA (deoxyribonucleic acid) is an organic molecule responsible for the storage and transmission of genetic information which is expressed by the production of varied proteins that compose the living being. Have you ever thought about extracting DNA from vegetal cells at home? With some simple ingredients and following the right procedures you will be able to extract and visualize the DNA of an onion. 
The students of “Adopt a Scientist”, after a conversation about the DNA molecule, conducted the activity oriented by  Daniel Onofre Vidal, postgraduate of the Medical School of Ribeirão Preto (FMRP/USP), and Rafaela de Barros e Lima Bueno, doctorate in Genetics by FMRP. Let’s try? 

-A big onion
-A kitchen knife (be very careful, ask an adult to help you) 
-Two glasses of 200ml 
-Hot water (flask, 60º C)
- Filtered water 
-Unscented dish detergent 
-Cold 92.8% ethanol (-10ºC, leave it for one hour in the freezer before starting the procedure) 
-Glass or wood thin stick (or a hard plastic straw) 
-Filter paper (coffee)
-Crushed ice
-A bowl for the ice 
-Chop the onion (0.5 cm pieces) and crush it using the pestle. Pour in the glass four spoons of the detergent and add a teaspoon of salt and add water until half glass, stir until dissolving completely. Put the chopped onion in the glass with the detergent/salt solution and put it in a water bath for 15 minutes. 
-Take the glass off the water bath and quickly chill it, putting it in the ice bowl for 5 minutes.   
-Sieve the mixture using the paper filter, and then collect the filtered in a clean glass. 
-Carefully add half a glass of cold ethanol to the filtered liquid, let it drain slowly through the glass edges. You will have two phases, the upper one, alcoholic, and the lower, aqueous.  
-Dive the stick into the glass and, stir it in round moves, mixing the phases. You will see some whitened strings which are clusters of DNA molecules. 

Understand what happens 
After the procedure is done, it is possible to easily visualize the small clusters that are the DNA filaments. Remember that naked eye visualization is possible because the DNA amount is large and the filaments are all grouped. 


When you grind, you break the cell wall, which is the extracellular structure that involves and protects the vegetal cell. 

The detergent helps to dissolve the lipid bilayer that composes the plasma membrane, the membranes of organelles and nuclear membrane that surrounds the nucleus.
The salt helps to keep the proteins dissolved in the liquid extracted, stopping them from precipitating with the DNA. 
 Water bath 
The heating in water bath aims the breakdown of membrane phospholipids and the partial denaturation of type DNAse enzymes, avoiding that DNA is cut in small fragments what would compromise a later extraction. 
The DNA is not soluble in ethanol (ethyl alcohol) that is why it promotes the clustering of the filaments, making them visible. The colder the ethanol, the less soluble is the DNA. 
Do you want a better result? 
Leave the solution in fridge for a couple of hours. The visible DNA amount will increase considerably.  
Go further!
Is it possible to follow this script to extract the DNA of an animal cell? 


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