An Idiots Guide to DNA barcoding - 1.


This document is designed as a simple introduction to DNA barcoding for non-scientists. As such, we will need to introduce a few concepts and definitions that are necessary in order to understand this exciting and important new approach to the discovery, cataloging and monitoring of biodiversity. I will not go into any significant detail about modern molecular biology and the methods it employs. The object here is to explain a new subject that is at the cutting edge of biodiversity, molecular biology and bioinformatics research to non-specialists and to make it fun and interesting. So, lets not worry too much if we oversimplify some concepts in our quest to catalog and identify all living organisms on planet earth.

Background and a few definitions:


Taxonomy is the practice and science of classification. The word comes from the greek words for "order" and "science". Taxonomies or taxonomic schemes are composed of taxonomic units known as taxa (taxon in the singular) and arrange things to be classified in hierarchichal structures, typically related by subtype-supertype relationships.

Linnaean taxonomy is a method of classifying living things, originally devised by (and named for) Carl Linnaeus, although it has changed considerably since his time. The greatest innovation of Linnaeus, and still the most important aspect of this system, is the general use of binomial nomenclature, the combination of a genus name and a single specific epithet to uniquely identify each species of organism. For example, the human species is uniquely identified by the binomial Homo sapiens. No other species of organism can have this binomial. Prior to Linnaean taxonomy, animals were classified according to their mode of movement.

All species are classified in a ranked hierarchy, starting with kingdoms. Kingdoms are divided into phyla (singular: phylum) Phyla are divided into classes, and they, in turn, into orders, families, genera (singular: genus), and species (singular: species).

Linnean taxonomy is considered to be a natural classification system for living organisms as all living things are indeed descendend from a single common ancestor and have diverged from one-another through a series of speciation events though the process known as evolution. As a result, some groups of species are more closely related than others and might reasonably be classified within the same genus, family, order etc.

Evolution is the process of change in all forms of life over generations, and evolutionary biology is the study of how and why evolution occurs. An organism inherits features (called traits) from its parents through genes. Changes (called mutations) in these genes, occur randomly and can produce a new trait in the offspring of an organism. If a new trait makes these offspring better suited to their environment, they will be more successful at surviving and reproducing. This process is called natural selection, and it causes useful traits to become more common. Over many generations, a population can acquire so many new traits that it becomes a new species.