How DNA Can Be Extracted From Fruit | Genetics | Biology | FuseSchool

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How DNA Can Be Extracted From Fruit | Genetics | Biology | FuseSchool

Did you know that you share 50% of your DNA with a banana? You might be more closely related than you thought!

This is because all living cells contain genetic material in the form of the chemical DNA.

Each of your cells contains an incredible two metres of DNA! It is possible to fit all that DNA into a tiny cell because the DNA is extremely narrow, only about two nanometres, and it is tightly wound around proteins. You can find out more about DNA and its structure by watching this video.

Do you want to see what DNA looks like?
Well, it is possible, you just need to extract it from some cells. You can do this in the lab or even in your own kitchen. The easiest way to do this is to use some fruit. In this video will we go through the steps to show you how.

First, you need to choose your fruit. The best fruits to use are those that have plenty of DNA. Strawberries are a good choice, as are kiwi fruit.

You then blend or mash the fruit with salt water. This breaks apart the cells from each other. It also starts to break down the cell walls. Salt is used so that the DNA is more likely to clump together in the final stage.

The next stage is to pass the liquid through a sieve and collect the 'fruit soup'. This will contain all the strawberry cells with the DNA inside the nucleus.

To break apart the membranes surrounding the cell and the nucleus, and release the DNA, you add some detergent, such as washing-up liquid, to the soup. This ruptures the cell membranes.

Adding a pinch of protease enzyme will help break down the proteins the DNA is wound tightly around. The DNA will uncoil and will now be present in the mixture as long strings. You can use pineapple juice, contact lens cleaner or a pinch of meat tenderiser. These all contain protease enzymes.

You can’t yet see the DNA because it is dissolved in the mixture. To see the DNA you have to make it insoluble. To do this, you slowly pour ice-cold ethanol into the mixture.

The ethanol is at this low temperature to slow down the action of enzymes naturally present in the cell that will break down the DNA. In a normal healthy cell, these enzymes are usually kept separate from the DNA by the nucleus membrane, but you ruptured this in an earlier step.

Ethanol is less dense than water so it forms a layer on top of the fruit soup. The salted DNA is insoluble in ethanol, so will begin to precipitate out of the fruit soup at the boundary between the soup and the ethanol. It transforms from a dissolved solute into an insoluble substance in the ethanol layer.

You will see cloudy strings of DNA which you can remove by winding it around a wooden stick. And there you have extracted DNA!

You can then observe this DNA with a microscope or use it for other experiments.


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