![]() Now, on the slide, there'll be millions or tens of millions of these, of these fragments of DNA. Typically a few hundred bases long, maybe a little longer than that maybe as much as 1,000 bases long and we attach those, we chemically attach those to a slide. So how do you do that? The way Next Gen sequencing does, does it, is we take our, our template DNA, we chop it up into small pieces. Somehow you get to observe this and measure your DNA while all this is going on. Now if you could just watch this happening, then you wouldn't need to do what we're calling sequencing. So, you start with single strand DNA, and then with, you add lots of As, Gs, Cs, and Ts, and some DNA preliminaries and you can synthesize the, the complimentary strand. And of course when we copy, we use this rule of DNA that gGs always bind to Cs and As always bind to Ts. And it uses them to copy the DNA that you're trying to sequence. So DNA, it's copied by a molecule called DNA Polymerase which takes free nucleotides, those are As, Cs, Gs and Ts, that are just floating around in your cell or you can synthesize them so that they can be floating around in your test tube. So use DNA at the D, the mole, the molecular machinery that, that cells use for copying is a key tool in this process. So first for you to understand that all, that all these DNA sequencing technologies rely on taking a DNA template, the DNA that you want to sequence and copy. Most new of the DNA being, the vast majority of DNA being generated around the world today comes from second generation sequencing. That's still very new technology, and not, not at all mature. And in fact this now already been in some ways, or some, it's been superseded by a new generation of sequencing that, that looks at single molecules. ![]() But second generation sequencing or Next Generation Sequencing that I'm going to describe, came along in around 2007. That involved attaching DNA to a, to a tiny slide and, and then measuring other genomes by, by letting their DNA or RNA stick to that DNA. As time went on, in the 1990's there was a technology called DNA Microarrays that was invented, which wasn't exactly sequencing. And that's what we call Sanger Sequencing, and that's really the first generation of sequencing. And in the 1980s a number of, a number of companies put together automated DNA sequencers and let people use that technology to sequence things much faster and more efficiently than had ever been possible before. And those, that sequencing was the first very manual, very painstaking and slow. Back in the, or, in the 70s, 80s and 90s we used a technology, it was called Sanger Sequencing because it was invented by a scientist named Fred Sanger. So sequencing has undergone a number of different generations. But for now we call it NGS or Next Generation Sequencing. So next generation sequencing is a term we use to describe the very latest sequencing technology which has been around now since around 2007 and we'll probably come up with a better name for it, overtime. ![]() We're just going to cover the, the basics, but it's important that you have an idea of how sequencing works so you'll understand the data that you're looking at. ![]() In this section we're going to talk about Next Generation Sequencing.
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