Shotgun sequencing

In genetics, shotgun sequencing, also known as shotgun cloning, is a method used for sequencing long DNA strands. It is named by analogy with the rapidly expanding, quasi-random firing pattern of a shotgun.

The chain termination method of DNA sequencing (or "Sanger sequencing" for its developer Frederick Sanger) can only be used for fairly short strands of 100 to 1000 base pairs. Longer sequences are subdivided into smaller fragments that can be sequenced separately, and subsequently they are re-assembled to give the overall sequence. Two principal methods are used for this: primer walking (or "chromosome walking") which progresses through the entire strand piece by piece, and shotgun sequencing which is a faster but more complex process that uses random fragments.