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DNA Barcoding Workflow

Posted in Forensic Entomology & DNA Barcoding by paibiopai on March 28, 2011

Species identification through barcoding is usually achieved by the retrieval of a short DNA sequence – the ‘barcode’ – from a standard part of the genome (i.e. a specific gene region) from the specimen under investigation. The barcode sequence from each unknown specimen is then compared with a library of reference barcode sequences derived from individuals of known identity. A specimen is identified if its sequence closely matches one in the barcode library. Otherwise, the new record can lead to a novel barcode sequence for a given species (i.e. a new haplotype or geographical variant), or it can suggest the existence of a newly encountered species.

Various gene regions have been employed for species-level biosystematics, however, DNA barcoding advocates the adoption of a ‘global standard’, and a 650-base fragment of the 50 end of the mitochondrial gene cytochrome c oxidase I (COI, cox1) has gained designation as the barcode region for animals. This fragmentsize has been selected so that a reliable sequence read can be obtained by a single sequence pass in conventional cycle sequencing platforms. Shorter fragments of COI have also been shown to be effective for the identification of specimens with degraded DNA, however, where a 650-base sequence is not easily obtainable. In addition, the usability and robustness of COI in a standard highthroughput barcoding analysis have been extensively assessed.

Other researchers have suggested that alternate loci might also serve as a basis for species identification. For example, (more…)


Biological identifications through DNA barcodes

Posted in Forensic Entomology & DNA Barcoding by paibiopai on October 6, 2009

“Although much biological research depends upon species diagnoses, taxonomic expertise is collapsing. We are convinced that the sole prospect for a sustainable identification capability lies in the construction of systems that employ DNA sequences as taxon ‘barcodes’. We establish that the mitochondrial gene cytochrome c oxidase I (COI) can serve as the core of a global bioidentification system for animals. First, we demonstrate that COI profiles, derived from the low-density sampling of higher taxonomic categories, ordinarily assign newly analysed taxa to the appropriate phylum or order. Second, we demonstrate that species-level assignments can be obtained by creating comprehensive COI profiles. A model COI profile, based upon the analysis of a single individual from each of 200 closely allied species of lepidopterans, was 100% successful in correctly identifying subsequent specimens.When fully developed, a COI identification system will provide a reliable, cost-effective and accessible solution to the current problem of species
identification. Its assembly will also generate important new insights into the diversification of life and the rules of molecular evolution.” (Herbert et. al., 2003)

yoo, dna barcoding world has just begun.. all aplications regarding this thing are still unravelled.. now, it’s time for us to make a breakthrough,,, yeah..

you know, it’s my thesis topic,, dna barcode in (more…)

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