What does DNA do?

The DNA code contains instructions needed to make the proteins and molecules essential for our growth, development and health.

  • DNA provides instructions for making proteins (as explained by the central dogma).
  • The sequence of the bases, A, C, G and T, in DNA determines our unique genetic code and provides the instructions for producing molecules in the body.
  • The cell reads the DNA code in groups of three bases. Each triplet of bases, also called a codon, specifies which amino acid will be added next during protein synthesis.
  • There are 20 different amino acids, which are the building blocks of proteins.
  • Different proteins are made up of different combinations of amino acids. This gives them their own unique 3D structure and function in the body.
  • Only 61 of the 64 codons are used to specify which of the 20 amino acids is next to be added.
  • There are three codons that don’t code for an amino acid. These codons mark the end of the protein and stop the addition of amino acids to the end of the protein chain.

The codon wheel above can be used to translate DNA codons into amino acids. Find the first letter of your sequence in the inner circle and work outwards to see the corresponding amino acid, for example ATG = methionine.
Image credit: Genome Research Limited

  • Examples of proteins include keratin, the protein in your hair, and haemoglobin, the oxygen-carrying protein in your blood.
  • Although a major function of the genome, less than two per cent of the human genome provides instructions for making proteins.
  • The rest of the genome, which is called non-coding DNA, has a variety of functions. These include regulating when proteins are made and controlling the packaging of DNA within the cell.
  • However, there is still much we have to learn about the function of non-coding DNA. 

This page was last updated on 2015/01/15