Rosalind Franklin and DNA

in honour of Rosalind Franklin, here’s how to how to extract DNA from Kiwifruit in your own Kitchen. repeated below in case links die.

You will need:

1. A ripe Kiwi fruit.
2. Table salt.
3. Non concentrated washing up liquid.
4. Knife and a chopping board.
5. Measuring scales.
6. A measuring jug.
7. A teaspoon (5 ml).
8. Small bowl.
9. A large sauce pan full of hot water (not boiling ??” about 60 degrees).
10. A large sauce pan full of ice.
11. Coffee filter and filter funnel.
12. A tall, thin plain glass.
13. Some thin wire (fuse wire).

What to do:

1. Put the bottle of methylated spirits in the ice.

2.
Make up a solution of 3 grams of salt, 10 ml of washing up liquid and
100ml of water. Measure 3 grams of salt . You may find that your scales
will weigh out a minimum of 25 grams. If this is the case add 80 ml of
washing up liquid (16 measuring spoons) and make up to just less than
one litre. Stir your mixture thoroughly (avoid froth) to dissolve the
salt.

3. Peel and chop one Kiwi fruit. Scoop this into the small bowl and add 100 ml of the salt ??” detergent mix.

4. Put the bowl containing the mixture into the saucepan of hot water and leave for 15 minutes.

5.
After 15 minutes pour the mixture into the coffee filter, and catch the
liquid that filters through in the tall glass. You will need about one
fifth of a glass.

6. Very carefully drizzle the ice cold meths
down the inside of the glass so that it forms a purple layer on top of
the green layer. When there is about a fifth of a glass of meths (i.e.
two fifths including the green liquid) put the glass on the table and
watch what happens.

7. After a few moments you should see a
white layer beginning to form at the boundary between the green and the
purple layers. If you have done it correctly you will see that the
layer is made up of a filament ??” DNA from Kiwi fruit.

8. Try scooping the DNA out with a loop of thin wire ??” purple white goo – the molecules of life.Here’s the explanation:

DNA
is found in every cell of every living thing, but it is difficult to
get it out and disentangle the DNA from the protein inside the cells.

The
composition of Kiwi fruit allows the DNA to be extracted without a
great deal of effort, but not all things do. By chopping the Kiwi fruit
and letting it soak in the detergent and salt the first part of the
problem is solved. The detergent strips away the cell membranes that
cover the inside of the cell and lets the internal goo escape. The kiwi
fruit needs to be chopped fine enough to get the cells broken open, but
this should not be overdone or the DNA will be smashed.

The
second part of the problem, getting rid of the protein that has stuck
to the DNA is all done by the Kiwi fruit. The Kiwi fruit already
contains a lot of a special enzyme called a proteinase. Enzymes are
like small molecular machines that do many things ??” the enzymes in
washing powder digest fat for example. The proteinase enzyme attacks
the proteins clinging to the DNA and breaks them up thereby releasing
the DNA. Rosalind Franklin tried oranges, but oranges do not contain
enzymes and therefore she failed to make DNA from them. She and Raymond
Gosling finished up having a food fight with the residue of their
efforts.

A woman after my own heart.

The green
layer that is produced in the glass is full of DNA as well as lots of
broken up proteins and other things. When the cold meths is poured onto
the green layer, the DNA dissolved in the water layer at the bottom of
the glass is turned into a solid as the DNA cannot remain in the
solution. Little bubbles may form between the two layers and drag the
strands of DNA up into the meths ??” the bubbles may be caused by the
temperature difference between the layers, making the air dissolved in
the green layer come out of the solution. � BA

Finally, may I echo the sentiment expressed in the website:

We hope that this information has been useful to you.