Extracting DNA in your kitchen

DNA in all organisms provide instructions about how to grow and go about millions of cellular processes each day.Researchers separate the DNA from the rest of the cell and examine how it interacts with proteins and other parts of the cell. Follow these instructions to learn how to extract DNA from an onion.
What you need

To do this experiment you will need to gather:

half an onion
salt
washing-up detergent
methylated spirits
warm water
coffee filter paper
a toothpick or wooden skewer
a knife and chopping board
a strainer or sieve
a blender or food processor
a clear drinking glass
What to do

Ask an adult to help you roughly chop the onion and put it in the food processor. Dissolve one teaspoon of salt in half a cup of warm water, add to the onion and process for one minute. Strain the mixture through the sieve into a cup, pressing the liquid out using the back of a spoon. Add one teaspoon of washing-up liquid and stir. Leave for five minutes, stirring occasionally. Pour the mixture through the coffee filter into a clear glass. Let it drip through; you can squeeze the filter gently to speed this up. With an adult’s help, carefully pour enough methylated spirits down the side of the glass to form a one-centimetre layer on top of the onion solution. You should see a white fluffly layer form between the onion solution and the methylated spirits. Gently swirl the toothpick or skewer through the mixture and you will see little white strands moving around. These are bits of onion DNA! You can also twist the toothpick and, if you are careful enough, you should be able to lift out some blobs of DNA. It looks almost exactly like white snot!

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To start with, we had to break the cells open. The blender broke the onion into single cells. The detergent helped dissolve some of the chemicals in the cell membranes (the skin around the cell), letting the DNA and other chemicals out.

Once the DNA was removed from the cells, we needed to separate the DNA from the other chemicals. DNA dissolves in water, but it doesn’t dissolve in alcohol. Adding methylated spirits (which is almost pure alcohol) causes the DNA to stop being dissolved in the onion liquid and become solid, forming the white strands you saw.

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