<P> In bacteria and archaea, ITS is located between the 16S and 23S rRNA genes . On the other hand, there are two ITS's in eukaryotes; ITS1 is located between 18S and 5.8 S rRNA genes, while ITS2 is between 5.8 S and 26S (in plants, or 28S in animals) rRNA genes . ITS1 corresponds to the ITS in bacteria and archaea, while ITS2 originated as an insertion that interrupted the ancestral 23S rRNA gene . </P> <P> Genes encoding ribosomal RNA and spacers occur in tandem repeats that are thousands of copies long, each separated by regions of non-transcribed DNA termed intergenic spacer (IGS) or non-transcribed spacer (NTS). </P> <P> Each eukaryotic ribosomal cluster contains the 5' external transcribed sequence (5' ETS), the 18S rRNA gene, the ITS1, the 5.8 S rRNA gene, the ITS2, the 28S rRNA gene, and finally the 3' ETS . </P> <P> During rRNA maturation, ETS and ITS pieces are excised . As non-functional by - products of this maturation, they are rapidly degraded . </P>

Nuclear ribosomal internal transcribed spacer (its) region as a universal dna barcode