Vector maps contain all the information that you need to know in order to used a plasmid as a molecular tool.

The vector map indicates the different genes and genetic parts as colorful bars along its length. Usually there are two numbers indicating the beginning and end of the gene. These numbers refer to the distance, in base pairs, from the zero point of the plasmid. The zero point is an arbitrary position on the plasmid. In addition to he genes, the plasmid map depicts the various restriction sites. These are the positions where restriction enzymes cut the plasmid. The number in brackets indicates how many of these sites can be found on the plasmid.

A sample of the vector map shown as a circular structure with genes inside shown as colored arrows. The names of the restriction enzymes and their working sites in the vector are also shown.

Figure: Example of a vector map

The distance to the zero point can be used to make precise predictions about the size of DNA fragments. If you use restriction enzymes to cut a plasmid in two positions, you can determine the length of the resulting fragment with the positions of the restriction sites.