ITS2 sequences share a common core of secondary structure, while ITS1 structures are only conserved in much smaller taxonomic units. Regardless of the scope of conservation, structure-assisted comparison can provide higher resolution and robustness. Mycological barcoding The ITS region is the most widely sequenced DNA region in molecular ecology of fungi and has been recommended as the universal fungal barcode sequence. It has typically been most useful for molecular systematics at the species to genus level, and even within species (e.g., to identify geographic races). Because of its higher degree of variation than other genic regions of rDNA (for example, small- and large-subunit rRNA), variation among individual rDNA repeats can sometimes be observed within both the ITS and IGS regions. In addition to the universal ITS1+ITS4 primers used by many labs, several taxon-specific primers have been described that allow selective amplification of fungal sequences (e.g., see Gardes & Bruns 1993 paper describing amplification of basidiomycete ITS sequences from mycorrhiza samples). Despite shotgun sequencing methods becoming increasingly utilized in microbial sequencing, the low biomass of fungi in clinical samples make the ITS region amplification an area of ongoing research. References External links University of Washington Laboratory Medicine: Molecular Diagnosis | Yeast Sequencing ITSone DB ITS2 database (Schultz et al.) DNA Phylogenetics