What does DNA look like?
Surprisingly, while the DNA molecule is very long, it is stunningly simple. DNA looks like an incredibly long twisted ladder. This shape is called a double helix.
The sides of the ladder are a linked chain of alternating sugar and phosphate molecules. The rungs connect to the sugar molecules and are known as bases.
There are four bases - adenine (A), thymine (T), guanine (G) and cytosine (C). Each rung is made up of two bases that link together. Because of their chemical nature, A will only link with T and G will only link with C.
DNA from all living organisms is made of the same sugar and phosphate molecules and the same four bases. Whether DNA is in your cells, those of a cactus, of a worm or a bacterium, it is made of the same chemicals and has the same structure.
The only difference is the order or the sequence of the bases in the DNA molecule. It is this sequence that is referred to as the genetic code, and why it is sometimes called the code of life.