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.

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.

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.

How can we process 100,000 specimens a year?

Technology development is part of DNA barcoding projects. Major DNA barcoding facilities are now processing up to 100,000 specimens a year. These facilities rely on the latest technology in DNA sequencing, automation and data analysis to deliver rapid, cost-effective assembly of barcodes.

The International Barcode of Life Project (iBOL), which aims to analyse 5 million specimens over 5 years, is developing technology that can identify species rapidly and inexpensively. Others, like the Consortium for the Barcode of Life (CBOL), envisage developing technologies including a hand-held scanner that could assemble DNA barcodes on the spot. Such technology would make barcoding a task that could be performed by any interested person, anywhere, at any time.

Published 24 June 2009