D.I.Y DNA
A 'quick and easy' recipe for making DNA from a kiwi
fruit, using equipment and chemicals commonly found in the kitchen.
Precautions and safe working:
It is your responsibility to carry out a proper and sufficient
risk assessment before conducting this experiment.
The equipment and materials used are commonly found around the
house and so are not unfamiliar hazards, but several are
potentially hazardous.
Sharp: Kitchen knives and blender blades.
Flammable: Methylated Spirits.
Toxic: Methylated Spirits - if swallowed.
What you will need:
- Kiwi fruit (a ripe one works best)
- Salt (standard, pre-ground table salt works fine)
- Washing up liquid (A supermarket own brand is perfect. The cheaper the better,
as expensive brands have a lot of additives that interfere with the extraction)
- Knife
- Kitchen blender/liquidiser (or chop the Kiwi fruit into small pieces by hand).
- Chopping Board.
- Measuring Jug.
- Set of Measuring Spoons.
- Small Bowl.
- Honey jar (or other wide mouthed, lidded container).
- Bowl of warm water (about 60°C).
- Container of ice.
- Bottle of Methylated Spirits.
- Champagne Flute (or any tall, skinny glass).
- Paper clip or piece of fuse wire.
- Cafetiere or Coffee Filter Papers and a Coffee Filter Holder or Small Kitchen
Funnel.
What to do:
- Put the bottle of methylated spirits in the ice, to cool it
down.
- In a wide, lidded jar (one pound honey jars are perfect) mix
a heaped quarter teaspoon of salt and 100mls of water. Replace
the lid and swirl the jar to dissolve the salt. Add 3/4 of a teaspoon
of washing up liquid, replace the lid, gently swirl to mix the
contents, do not froth. Place the jar in the bowl of warm water.
- Peel a kiwi fruit and coarsely chop it into small pieces in
a blender/liquidiser (or by hand). DO NOT reduce it to a mush.
Scoop the pieces into the honey jar with the water, salt and washing
up liquid. Replace the lid and swirl the jar to mix the contents.
- Replace the jar in the bowl of warm water and leave for 15 minutes.
- Pour the green mush from the jar into a cafetiere and use the
plunger to push the solid material towards the bottom of the jug.
Only push the filter about half way through the mush. Pour off
the liquid into a champagne flute. Alternatively pour the green
mush from the honey jar into a coffee filter (in a coffee filter
holder or small kitchen funnel) and catch the liquid that runs
through, in a champagne flute. If the flow of liquid become very
slow then use a fresh filter paper. You will need between 1/5 and
1/4 of a glass of liquid.
- Very carefully run the ice-cold methylated spirits down the
inside of the champagne flute so that it forms a purple layer on
top of the green layer. Add about as much methylated spirits as
there is green liquid, set the glass down and watch.
- Almost immediately you should see a fluffy white layer beginning
to form at the boundary between the green and the purple liquids.
This is the DNA that you have extracted from your Kiwi fruit. After
a few minutes the DNA will probably float to the surface of the
methylated spirits.
- It may be possible to scoop the DNA out of the liquid by using
a loop of wire, such as piece of bent fuse wire or a paper clip.
Be sure to thoroughly wash all the equipment you have used
before using it for other purposes.
What is going on?
All the cells of the Kiwi fruit contain DNA. Slicing, chopping and
blending the fruit breaks open many of the cells and allows the
detergent/water/salt mixture to enter the cells and dissolve their
contents, including the DNA. The salt helps dissolve the cell
contents in the water, while the detergent helps breakdown the
fatty membranes in the cells, making the extraction more efficient.
The DNA
molecule is very fragile so it is important not to 'blend' the
fruit for too long, or shake the honey jar too vigorously.
Filtering the juice removes large bits of debris.
Finally, DNA is not soluble in alcohol, so floating a layer of ice
cold methylated spirits (alcohol) over the solution of DNA causes the
DNA at the interface between water and alcohol to come out of
solution, where it becomes visible as fluffy white threads.
