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<p><font size="4">[[Sequencing technology]]<br />[[Sequencing companies]]<br />
[[Sequencing assembly program]]<br />
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<p><font size="6">What is sequencing?<br />
<font size="3">Sequencing means to determine the order of signals in a polymer.</font> <br />
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</font><font size="3">In genetics and biochemistry, <strong>sequencing</strong> means to determine the primary structure (sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a <strong>sequence</strong> which succinctly summarizes much of the atomic-level structure of the sequenced molecule. </font></p>
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<h3><span class="mw-headline">Sanger sequencing</span></h3>
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<div style="WIDTHwidth: 162px" class="thumbinner"><img class="thumbimage" border="0" alt="Part of a radioactively labelled sequencing gel" width="160" height="332" src="http://upload.wikimedia.org/wikipedia/commons/c/cb/Sequencing.jpg" />
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<div style="FLOATfloat: right" class="magnify"><img alt="" width="15" height="11" src="http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png" /></div>
Part of a radioactively labelled sequencing gel</div>
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<p><font size="3">In chain terminator sequencing (Sanger sequencing), extension is initiated at a specific site on the template DNA by using a short oligonucleotide 'primer' complementary to the template at that region. The oligonucleotide primer is extended using a DNA polymerase, an enzyme that replicates DNA. Included with the primer and DNA polymerase are the four deoxynucleotide bases (DNA building blocks), along with a low concentration of a chain terminating nucleotide (most commonly a <strong>di-</strong>deoxynucleotide). Limited incorporation of the chain terminating nucleotide by the DNA polymerase results in a series of related DNA fragments that are terminated only at positions where that particular nucleotide is used. The fragments are then size-separated by electrophoresis in a slab polyacrylamide gel, or more commonly now, in a narrow glass tube (capillary) filled with a viscous polymer.</font></p>
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<div style="WIDTHwidth: 182px" class="thumbinner"><img class="thumbimage" border="0" alt="View of the start of an example dye-terminator read (click to expand)" width="180" height="42" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/44/Sanger_sequencing_read_display.gif/180px-Sanger_sequencing_read_display.gif" />
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View of the start of an example dye-terminator read (click to expand)</div>
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<h3><span class="mw-headline">Pyrosequencing</span></h3>
<p><font size="3">Pyrosequencing, which was originally developed by Mostafa Ronaghi, has been commercialized by Biotage (for low throughput sequencing) and 454 Life Sciences (for high-throughput sequencing). The latter platform sequences roughly 100 megabases in a 7-hour run with a single machine. In the array-based method (commercialized by 454 Life Sciences), single-stranded DNA is annealed to beads and amplified via emPCR. These DNA-bound beads are then placed into wells on a fiber-optic chip along with enzymes which produce light in the presence of ATP. When free nucleotides are washed over this chip, light is produced as ATP is generated when nucleotides join with their complementary base pairs. Addition of one (or more) nucleotide(s) results in a reaction that generates a light signal that is recorded by the CCD camera in the instrument. The signal strength is proportional to the number of nucleotides, for example, homopolymer stretches, incorporated in a single nucleotide flow. [1]</font></p>
<p><span style="font-size: medium"><b>Synthesis based sequencing by Illumina</b></span></p>
<p><font size="3">Solexa, now part of Illumina developed a sequencing technology based on reversible dye-terminators. DNA molecules are first attached to primers on a slide and amplified so that local clonal colonies are formed (bridge amplification). Four types of ddNTPs are added, and non-incorporated nucleotides are washed away. Unlike pyrosequencing, the DNA can only be extended one nucleotide at a time. A camera takes images of the fluorescently labeled nucleotides then the dye along with the terminal 3' blocker is chemically removed from the DNA, allowing a next cycle. The final product of the SBS is many [[DNA reads]].</font> </p>
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<h2><span class="mw-headline">RNA sequencing</span></h2>
<li><font size="3">Sequence motif </font></li>
<li><font size="3">[http://sequenceome.org Sequenceome.org] </font></li>
<li><font size="3">[http://glycome.net Glycome.net]</font> </li>
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<p><a id="References" name="References"></a></p>
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<li id="_note-0"><strong><a title="" href="http://en.wikipedia.org/wiki/Sequencing#_ref-0">^</a></strong> <a class="external text" title="http://www.stenutz.eu/sop" rel="nofollow" href="http://www.stenutz.eu/sop">A practical guide to structural analysis of carbohydrates</a> </li>
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