What is DNA barcode

What is DNA barcoding?

Ten reasons for Barcoding (pdf, English)

Each of us knows the industrial barcodes (barcodes) that identify each product in the trade individually. Analogous to these barcodes, certain short gene segments - so-called DNA barcodes - are also unique for each species. DNA barcoding has become the global standard for the rapid and reliable genetic identification of species in animals, plants and fungi

Using a short DNA sequence of a special marker gene, the mitochondrial COI gene, almost all animal species (e.g. birds, butterflies, fish, flies, etc.) on earth can be identified. The species identification of land plants is carried out using two different gene regions in the chloroplasts, matK and rbcL. Fungi can be identified based on the ITS region. The aim of DNA barcoding is to build a publicly accessible reference database with species-specific DNA barcode sequences. With the help of DNA barcoding, individuals from particularly difficult to identify and species-rich groups can be diagnosed, e.g. special developmental stages (spore, egg or larva) and even parts and fragments of organisms (fly leg, root, fungal hypha or hair). This method enables even non-specialists to quickly, inexpensively and reliably identify species with a wide range of applications.

Steps to create a DNA barcode database

  1. DNA barcode projects can obtain their samples from various sources: animal, plant and fungal material can be obtained from various public and private collection archives (e.g. natural history museums, zoos, botanical gardens, seed banks, etc.), provided the DNA is still preserved . However, GBOL is also dependent on the cooperation of highly motivated, experienced species experts who collect and determine sample material in the field and conserve it for molecular analysis.
  2. Taxonomic data and all collected data are recorded for each sample (e.g. collection location and date, geographical coordinates, collection method, name of the taxon expert, etc.).
  3. Each copy is photographed.
  4. The specimen copies are handed over to the respective collection archives of the GBOL institutes.
  5. In the laboratory, technical staff isolate a small piece of tissue from the specimen and extract DNA from it.
  6. The process of PCR (polymerase chain reaction) is used to enrich / replicate the specific DNA barcode region.
  7. The finished PCR product is sequenced using sequencing robots. A DNA barcode sequence consists of a sequence of four letters over a few hundred positions (e.g. CAATCGGTAA ...), which represent the four nucleic acids ( A.denin, Guanin, Thymin, and C.ytosine) of the DNA.
  8. The sequence and metadata (collection data, taxonomy, photographs, storage location and literature) of the samples are checked for quality and completeness by GBOL scientists.
  9. Each species profile including the DNA sequence is fed into the global reference database for DNA barcodes "BOLD - Barcode of Life Data Systems Database". BOLD is a publicly accessible online platform which, in addition to the DNA barcodes, also provides data on the location and collector of the sample and relevant information on the taxonomy, storage location, photos and literature. BOLD also offers the user multiple application functions such as species identification of sequences of unknown individuals, interpretation of relationships and species distribution maps.