DNA libraries
Before sequencing a genome, researchers make a copy of the information that can be stored and used as a reference over and over again. This is called a DNA library. Like your local library, a DNA library is a collection of information: in this case, encoded in DNA molecules.
There are many types of libraries. The Human Genome Project worked mostly with bacterial libraries, which can store and copy large DNA fragments - hundreds of thousands of letters long - or smaller fragments (a few thousand letters). Each bacterial cell stores an individual fragment of the genome. You need many bacteria to store all the genome of complex animal!
To prepare for sequencing, the bacteria are spread out onto plates of nutrients, where they grow and multiply. They can be seen as spots or colonies on the plates. Each of the bacterial colonies will contain many bacteria with the same piece of inserted DNA. This process is called DNA cloning.
Many of these processes are very boring for people to do in large quantities, so the Sanger Institute Robotics and Automation team have created robots to do as much of the work as possible.
