How do I know if my plasmid is a high- or low copy number type?
Find out which origin of replication your plasmid contains, and look at the table below for classification into high-copy or low-copy types. This table can also be found online at the QIAGEN Plasmid Resource Center in the section 'Growth of bacterial cultures; Plasmid Copy Number' . A way to determine experimentally if the copy number of your plasmid is high or low is to perform a miniprep. A high-copy plasmid should yield between 3-5 ug DNA per 1 ml LB culture, while a low-copy plasmid will yield between 0.2-1 ug DNA per ml of LB culture.
Origins of replication and copy numbers of various plasmids and cosmids
|DNA construct||Origin of Replication||Copy number||Classification|
|pUC vectors||pMB1*||500–700||high copy|
|pBluescript® vectors||ColE1||300–500||high copy|
|pGEM® vectors||pMB1*||300–400||high copy|
|pTZ vectors||pMB1*||>1000||high copy|
|pBR322 and derivatives||pMB1*||15–20||low copy|
|pACYC and derivatives||p15A||10–12||low copy|
|pSC101 and derivatives||pSC101||~5||very low copy|
* The pMB1 origin of replication is closely related to that of ColE1 and falls in the same incompatibility group. The high-copy plasmids listed here contain mutated versions of this origin.