These letters are arranged in three-letter words, known as codons. Each codon codes for one of the 20 amino acids. Amino acids are the basic building blocks of protein. Proteins are long strings of amino acids, which twist and fold up against themselves to form complex shapes. Most amino acids have several different codons which can code for them.
Some amino acids have only one possible codon.
Just like words in a real sentence, the words in the DNA code require punctuation in order to make sense. These are like full stops at the end of a sentence. The following gives an outline of these steps in a human cell. Although each cell has all the DNA required for a whole organism, not every protein is made in every cell all the time. Only certain proteins are needed by a cell at any one time.