Proteins are made up of several amino acids. The sequence of amino acids present in the protein is determined by the sequence of nucleotides in the mRNA. Each set of three nucleotides on the mRNA codes for one amino acid. This process is called translation. Translation is carried out by ribosomes.

In prokaryotic organisms, several ribosomes attach to a single stretch of mRNA and carry out the process of translation. This complex structure formed by the joining of several ribosomes to a single mRNA is called polyribosomes or polysomes.

Polysomes carry out translation and result into the production of several copies of the same protein in the prokaryotes.