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 has fallen to tens of thousands of dollars in late 2009.

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.  

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. 

Oxford Nanopore is developing a system that removes this labelling step, allowing for a step-change improvement in costs and speed of DNA sequencing.  Nanopores are expected to deliver long read lengths, allowing for simplified informatics.