Cosmids are created by combining parts of the lambda
chromosome with parts of plasmids.
The cosmid pJB8 contains:
Cosmids can carry up to 50 kb of inserted DNA.
- an origin of replication (ori)
that allows it to replicate as a bacterial plasmid,
- a cos gene for packing phage DNA into protein coats,
- an ampicillin resistance gene (amp),
- a region containing restriction sites for cloning
(BamHI, EcoRI, ClaI, and HindIII).