Methods for DNA sequencing were first published in 1977 by Maxam/Gilbert and Fred Sanger.  Since this time, new methods have been developed that have improved the speed and cost of sequencing by many orders of magnitude. The first human genome sequence cost an estimated $3 billion. Publications in late 2008 estimate the current cost (of consumables only) to be in the region of $250-500k and this fell to tens of thousands of dollars in late 2009.  In 2011 it is possible to purchase a sequence of a human genome for $10k.  Sequencing costs are illustrated here at the NHGRI website.

Current methods that are most commonly used include sequencing by synthesis and sequencing by ligation.  These methods utilise fluorescent chemicals to label individual DNA bases, which are then identified using optical instrumentation.   A range of instruments are available, ranging from high-yield instruments that tend to be more complex and have high capital costs, to desktop instruments that currently offer lower yields but have lower capital costs.

Sequencing methods produce a series of segments of DNA code, referred to as 'reads'.  These are then assembled to form a complete genome sequence using various computational methods.  'Read length' refers to the number of DNA bases that is included in each segment; longer read lengths in general allow easier assembly of the genome.  Current sequencing methods may be divided into 'short read' and 'long read', although the gap between these methods is closing.  

Most available DNA sequencing technologies also rely on the need to amplify the sample DNA in order to achieve a significant enough sample for sensing.  This complex procedure is improving in simplicity but still has the capacity to introduce errors and bias into the sample before sequencing.

Oxford Nanopore is developing a system that removes the need for amplification and optical labelling and uses an electronics-based platform, GridION, to sequence and analyse the DNA.  This allows for improvements in yield and cost through scalability, but also allows simplification and versatility of the overall workflow of DNA sequencing.  

GridION is also designed for the analysis of other single molecules.  For more information on potential applications please visit the following pages: other applications