Next-generation sequencing (NGS), developed in 2005, allows for the simultaneous sequencing of numerous DNA samples quickly and cost-effectively. Key NGS technologies include Roche/454 FLX, Illumina/Solexa, and Applied Biosystems SOLiD, each utilizing distinct methods for sample preparation, amplification, and result analysis. These techniques, which involve processes like pyrosequencing and bridge PCR, enable high-throughput sequencing of DNA with varying read lengths and are revolutionizing genomic research.

1. Next generation sequencing
By Shahzeb khan

2. NGS
Also known as high-throughput DNA
sequencing tehniques.
Developed in 2005.
Perform numerous sequencing reactions
simultaneously.
Less expensive.
Quick.

3. NGS
 widely used sequencers;
1. The bead-amplification sequencing
(Roche/454FLX).
2. Sequencing by synthesis (Illumina / Solexa
Genome analyzer).
3. Sequencing by ligation (Applied Biosystems
SOLID System)

4. NGS
Roche 454
Ilumina/
solexa GA
SOLID

5. NGS
All NGS systems have three common features differing
on the techniques used;
1. Sample preparation(fragmentation/ligation of
adapters).
2. Amplification(bridge PCR/emulsion PCR).
3. Analysing results.

6. UNIVERSAL LIBRARY PREPARATION.

7. ROCHE/454FLX
First next-generation sequencing technology.
By 454 Life Science (Branford, CT, USA) in 2005.
Read length 700 Bp.
Use pyrosequencing technique.
Sequencing by synthesis principle.

8. ROCHE/454FLX
EMULSION PCR
Adapters, ligated at both end of DNA fragments.
Fragments are mixed with small 28-µm streptavidin-
coated beads.
Beads have sequences complementary to adapters.
For fragment amplification all required reagents are
provided in droplets of water in oil mixture .
Each bead now carry millions of sequences.
Each bead must carry a unique sequence.

9. ROCHE/454FLX

10. ROCHE/454FLX
SEQUENCING
Beads incubated with DNA-polymerase are loaded onto
PTP well.
PTP wells are filled with 1µm bead having sulfurylase
and leuciferase.
PTP wells are loaded onto 454FLX sequencer provided
with dNTPS and buffers.
Four nucleotides are added in sequential manner.
When a nucleotide is incorporated a light signal is picked
by CCD camera.

11. ROCHE/454FLX

12. ILLUMINA / SOLEXA GENOME ANALYZER
introduced by Solexa in 2006 (San Diego, CA, USA)
read length to up to 100 Bp.
Use bridge PCR technique.
Sequencing by synthesis principle.

13. ILLUMINA / SOLEXA GENOME ANALYZER
BRIDGE PCR
Adapters, ligated at both end of DNA fragments.
Fragments, immobilised on a flow cell having
primers complementary to adapters.
A bridge structure is created.
After several PCR cycles 1000s of s.s DNA
fragments are synthesised.

14. ILLUMINA / SOLEXA GENOME ANALYZER

15. ILLUMINA / SOLEXA GENOME ANALYZER
SEQUENCING
We need homogenous population of strands for
sequencing.
The cluster of fragments are supplied onto another
surface having primers.
Four reversible blocked nucleotides (3´-OH is chemically
blocked) are added.
After the acquisition of images in each cycle, the 3´-OH
blocking group is chemically removed.
 Another cycle can be initiated.

16. ILLUMINA / SOLEXA GENOME ANALYZER

17. APPLIED BIOSYSTEMS SOLID
Developed in late 2007.
Use pyrosequencing technique for amplification.
Sequencing by ligation principle.

18. APPLIED BIOSYSTEMS SOLID
Amplification of fragments through EMULSION PCR as
discussed earlier.
SEQUENCING
Beads having unique DNA fragments are fixed on a flow
cell via 3´- modification of DNA strands.
Primers are annealed complementary to adapters.
Fluorescently labelled octamers are added to the
mixture.
Each octamer also holds one of four fluorescent dyes.

19. APPLIED BIOSYSTEMS SOLID
Octamer whose specific dinucleotide(usually 4,5
nucleotide) is matched with a template is hybridized and
than ligated by ligase.
An image is taken at this stage.
 Last three bases(6,7,8) of octamer are chemically
removed, so five bases of octamer are left behind.
The above step is repeated 10 times.
The same cycle is repeated with another primer(n-1) for
bases (3,4) and so on.

20. APPLIED BIOSYSTEMS SOLID

21. APPLIED BIOSYSTEMS SOLID