Internal Transcribed Spacer
A small (~550bp) stretch of DNA separating the genes encoding the large and small subunits of ribosomal RNA. It is sometimes described as the ‘universal DNA barcode’ because it is present in all bacteria, archaea, plants, fungi and animals (but not viruses). Fungi have two different versions of ITS (ITS1 and ITS2), which are both present in many hundreds of copies in the genome.