DNA barcoding
DNA barcodes are short sequences from a standard region of the mitochondrial cytochrome c oxidase subunit 1 (CO1) gene. A simple method of obtaining a DNA barcode is described here.
What does DNA barcoding involve?
1. Extracting DNA from the sample specimen
In most cases, only a small amount of sample material (1–3 mm3 – about the size of a match head) is required for DNA barcoding. The way the DNA is extracted depends on the source of the sample material and how old it is.
Only a small sample is required
Typical specimen types and sizes used for DNA barcoding analysis as compared to a pencil head. (a), a lepidopteran leg; (b), a Daphnia; (c), a feather; (d), muscle tissue.
2. Copying the DNA
DNA is amplified using polymerase chain reaction (PCR). This increases the number of copies. Primers are used to amplify a specific region of the CO1 DNA barcoding gene
Find out more about the ideal barcoding gene.
3. Checking the DNA
Gel electrophoresis is used to check the size of the copied DNA fragments and ensure there is plenty of good quality DNA.
Gel electrophoresis: Pūkeko DNA
Gel electrophoresis is used to check the quality of the DNA sample, in this case, DNA from pūkeko.
4. DNA sequencing
The DNA fragments from PCR are cleaned to remove buffer salts or protein contaminants and then sequenced. This sequence produces a DNA barcode that is specific to the sample specimen. Find out more about DNA sequencing.
5. Comparing DNA barcodes
The newly sequenced DNA barcode is compared with barcodes from known species. This is done by entering the sequence into databases like GenBank, EMBL or the Barcode of Life Database (BOLD) and checking against their records.
Building DNA barcode reference libraries
There are a number of DNA barcode reference libraries. For example, the International Barcode of Life Project (iBOL) completed the BARCODE 500K program. Research organisations from 25 countries barcoded 500,000 species. Building on this success, iBOL has launched BIOSCAN, which will extend barcode coverage to 2.5 million species by 2026!
