Genes and proteins

Here is a DNA molecule. It looks like a twisted ladder. DNA molecules appear in the nucleus of almost every one of your cells. We can say that DNA is a cookery book. Parts of the DNA molecule are genes, and the genes are the recipes.

Who reads the recipes? The cell itself. Inside it, there are things that look like tiny devices that can read the genes, and cook what the recipes describe. Watch closely, now it's reading. The DNA chain opens up in the middle, like a broken zipper.

This way the device gets to decode the DNA. It reads the rungs. The recipe is a bit monotonous really. A, C, G, T, T, A, C, G, C... In the entire cookbook, there are only four letters.

They are the abbreviations for four different substances: adenine, thymine, guanine and cytosine. The order of the four substances tells which ingredients should be used. Just like the order of the letters in a word determines what word it is. And the order of the ingredients determines what will end up being 'cooked'. Here are the ingredients.

They are amino acids. There are twenty different amino acids in the human cell. When the machine decodes the DNA chain, the letters A, T, G and C tell what amino acids to use, and how to put them together. Here are the letters T, G, T. This is like a word, and the word marks an amino acid.

The next word is G, A, T. This too, is an amino acid. It connects to the first amino acid. And so it goes on: DNA is decoded - three letters at the time - and the device connects a long chain of different amino acids. Then the chain folds, and becomes a protein.

It is proteins that DNA is all about. The recipes in the cookbook are recipes for various proteins. Lots of proteins. From the twenty amino acids, the devices in the cell can build over twenty thousand different proteins. So, all the genes do is show the cell how to produce...

proteins? Yes, in fact it is. But it's an incredibly important task. Because proteins do lots of different things in the body. Without proteins we don't function at all.

If you have too much or too little of certain proteins, or if a protein has the wrong shape, you might get ill. When your muscles move, proteins are at work - special kinds that can contract, and expand. When you take a deep breath, and the oxygen goes through your lungs out to your blood - proteins are around carrying the oxygen to the cells. When you are hungry... ... or sleepy... ...

or in love... ... or when your body changes in puberty - it is all because of proteins. Proteins also control many of your characteristics. Like how tall you are, or what hair colour you have. They even play a role in your personality.

If you had had a different combination of proteins, you would have been somebody else. Your genes give you a unique mix of proteins, and a unique mix of proteins give unique characteristics. This is why no other person is exactly like you.