Friday, November 20, 2009
This video dedicated to my undergraduate degree in biology, in which it was never deemed necessary to introduce the fact that sequencing technology more sophisticated than the Sanger method exists. This is an animation explaining the process behind Helicos's new single-molecule sequencing technology. Like all other modern sequencing methods, this technique is based on short-read sequences-- DNA is replicated and then broken into millions of tiny fragments (25-50 base pairs at the low end), all of which are sequenced simultaneously. Given about 30-fold coverage of your genome, you can align these fragments to confidently reconstruct it as a single sequence.
Also of note, the Velvet algorithm is one cool sequence assembly program which, instead of aligning DNA fragments by simply looking for overlapping regions between them, plots all the fragment sequences generated onto a De Bruijn graph, and then uses principles of graph theory to condense them into a single sequence. Yay math!