DNA sequencing became a practical tool with the invention of the chain termination method by Fred Sanger and colleagues in the 1970's. This method is often called Sanger sequencing, or sometimes it's called first generation sequencing. And though the method, at first, was rather labor intensive, requiring manual intervention by a human, over the years, the method was also improved and automated. And it was packaged in to commercial products, like these machines that are illustrated in the picture on the right. It remained the dominant method for DNA sequencing all the way through the Human Genome Project, and Fred Sanger won a Nobel Prize for chemistry for this invention. The Human Genome Project used hundreds of first generation DNA sequencers. The story of the Human Genome Project and how it used DNA sequencing technology is really an amazing one. The technology was an important part of what made that project possible, and it was also an important part of what drove the competition between the two competing teams. But if the story of the Human Genome Project is really amazing, another amazing story is what's happened to DNA sequencing technology since the end of the Human Genome Project. And that story is summarized in this plot here. So here, the horizontal axis shows years since the year 2001, which is around the end of the Human Genome Project. And the vertical axis shows the cost of sequencing one human genome's worth of DNA, or so. And the cost is shown on a logarithmic scale, so each tic mark on this vertical axis is another factor of ten. So, one thing that I bet you notice when you look at this plot is that something very important seems to happen around the year 2007. That's the year that a new kind of sequencing technology started to be used in life science labs around the world. This new technology goes by a few different names. It's sometimes called next-generation sequencing, or it's sometimes called second-generation sequencing, to distinguish it from first-generation sequencing, which was Sanger Sequencing. But another good name for this technology is massively parallel sequencing, because the reason the technology is so inexpensive is because it's able to sequence many millions, or even billions of molecules of DNA all in parallel. All at the same time. We'll see later how it's actually able to do this. This plot is showing cost, but cost is only part of the story. Besides improvements in cost, there were also improvements in speed, in accuracy, and how easy it is to actually use these machines. And so over time, as a result of all these different improvements, DNA sequencers have really become the premiere tool for studying nucleic acids like DNA and RNA, which are crucial to many different phenomena in life science. There are thousands of these second generation sequencers deployed across the world. And all together, they're generating many, many petabytes of sequencing data per year.
