These small plasmids (2.7 kb, see figure fig:pucclon) have the pBR322 ampicillin resistance gene, the pBR322 origin of replication, and a portion of the lac Z gene of E. coli. Within the lac region is a polylinker sequence of unique RE recognition sites identical to those in the multiple cloning sites of M13 . They grow to a high copy number and can be amplified with chloramphenicol .
The pUC vector is linearized by EcoRI digest (see figure fig:pucclon) to generate termini of the vector that are compatible with the cohesive termini found in the insert fragment to be subcloned.
6 
l pUC18 were digested
in a volume of 20 l with 20 U (1 l)
EcoRI (New England Biolabs).
Figure 3.3: pUC plasmids, indicating restriction maps of polylinker
regions of pUC8, 9 and
18