What is DNA?

We've heard about DNA and seen pictures of its molecular structure, but what does it actually look like?

So you want to know what DNA looks like? Well this is where the spinach comes in again! We are going to prepare DNA from spinach. You could use anything else, like peas, chicken liver, you little brother or sister's big toe... But spinach works particularly well.

What do we need to do first? We need to break up the spinach into cells. We will use a very advanced piece of scientific equipment - the kitchen blender!

Place a pack of spinach leaves into a kitchen blender and add a little water. Blend, adding water as necessary, until you have a medium consistency soup. Pour some of your soup into a clear glass so it is about half full.

The membranes that hold cells together are made of a form of fat. When we clean our plates, what do we use to break down the grease and fat? That's right, washing up liquid, so we should be able to use washing up liquid to break down the fatty cell membrane.

Add washing up liquid to your soup. You need about one-quarter of the amount of soup. So if you have 4 volumes of soup, you add one volume of washing up liquid.
Now you need to stir well for about 2 minutes. Use a kitchen timer to time yourself.

You should now have disolved the cell membranes.

DNA is wound securely around proteins called 'histones'. Imagine the DNA as being like cotton wound round a cotton reel. So how can you get the cotton off the reel without damaging it too much? You could get hold of the end of the cotton and pull... But we can't do that with DNA - there is no way we can grab the end of the DNA and pull. How else could we get it off? We could smash the cotton reel!

Well we don't have a hammer small enough to smash the histones, but we can use an enzyme to eat the protein away. The enzyme we will use can be bought from supermarkets as 'meat tenderizer'. It's just a white powder!

Add about 2 teaspoons of meat tenderizer and stir slowly and gently for at least 5 minutes. You must be gentle so as not to break the strands of DNA. Use a kitchen timer to time yourself.

You should now have released the DNA into the solution. DNA is less soluble in a chemical called isopropyl alcohol (IPA) than it is in water so we need to get it into the IPA so that is 'precipitates' - that is it becomes solid rather than being in solution.

Very carefully add some isopropyl alcohol so it forms a layer on top of the spinach soup. The best way to do this is to hold a teaspoon so that the tip is just in the soup and pour the IPA gently into the spoon. It's a bit like making an Irish Coffee, where you form a layer of cream on top of your coffee.

Now watch what happens... You will see a white substance starting to form at the interface between the soup and the IPA. What is this white stuff??

It's DNA!

If you leave it for a few minutes you will see more DNA separating out and if you are lucky you can skim it off with the handle of your teaspoon. If you put it on some kitchen paper, you can let it dry out.

The DNA you prepare will be rather green - DNA is actually white, but your sample is contaminated with a protein called chlorophyll. Chlorophyll is the green colour in plants which captures energy from the sun and uses it to convert carbon dioxide from the air and water, into sugar.