The circle
A plasmid map draws the circular DNA as a ring, numbered clockwise from position 1 at the top. The total size is shown in the middle, in base pairs. Arrows show features and the strand they are on: clockwise arrows are on the top strand.
The parts most plasmids have
- Origin of replication (ori): lets the plasmid copy itself in the host. pUC origins give hundreds of copies per cell; p15A and pSC101 give fewer.
- Selection marker: a resistance gene, such as AmpR (ampicillin) or KanR (kanamycin), so only cells carrying the plasmid grow.
- Promoter: where expression of the insert starts, such as T7, lac, CMV or EF-1α. Check that it works in your host.
- Multiple cloning site (MCS): a short stretch packed with unique restriction sites for putting in your insert.
- Tags and terminators: His or FLAG tags, and a terminator after the insert.
Restriction sites
Sites listed on the map are usually the unique ones, which cut the plasmid only once. To clone, pick two unique sites in the MCS that do not also cut inside your insert. The Restriction Summary lists single cutters in any sequence, and the Restriction Map shows where they fall.
See your own plasmid
Paste a GenBank file into the Plasmid Map Viewer to draw its features and sites as a map.