Table 4.
Developments in next generation sequencing technologies and specifications compared with automated Sanger sequencing (adapted from Wellcome Trust, 2009).
| Technology | Description | Read length (bases) | Runtime (days per gigabase) | Cost ($ per 1000 bases)1 |
|---|---|---|---|---|
| Sanger sequencing (dideoxy sequencing or chain termination method) | DNA is used as a template to generate a set of fragments that differ in length from each other by a single base through the use of modified nucleotides (dideoxy nucleotides) that when integrated into a sequence, prevent the addition of further nucleotides. The fragments are then separated by size, and the bases at the end are identified, recreating the original sequence of the DNA. | 1000 | 500 | 0.10 |
| Next generation sequencing methods | ||||
| 454, Roche (www.my454.com) | DNA fragments are anchored to individual tiny beads placed into wells on a plate. Nucleotides are washed over the wells in waves and as they are incorporated into the new DNA strand by the DNA polymerase enzyme, the intensity of light given off is used as a measure of how many As, Ts, Cs and Gs have been incorporated. | 450 | 2 | 0.02 |
| Illumina, Solexa, now Illumina (www.illumina.com) | Single DNA fragments amplified in dense clusters on a hollow slide to provide stronger fluorescence signals. | 75 | 0.5 | 0.001 |
| SOLiD, ABI Life Technologies (www.appliedbiosystems.com) | Sequencing by oligonucleotide ligation and detection. Unlike other sequencing platforms, which rely on a DNA polymerase adding bases one by one to replicate a new DNA strand, SOLiD sequences by ligation. | 50 | 0.5 | 0.001 |
1Overall cost depends on the number of bases in the genes being sequenced.