The DNA is a long chain of building blocks, also called nucleotides (or bases). The nucleotides in the DNA are:
- Adenine (A),
- Cytosine (C),
- Guanine (G) and
- Thymine (T).
At first sight, the DNA seems to be a random sequence of As, Cs, Gs and Ts, but the order of these letters is highly important. In fact, the order of the letters defines the genetic code and determines whether a good protein is produced.