PUC18
pUC19 is one of a series of plasmid cloning vectors created by Joachim Messing and co-workers. The designation "pUC" is derived from the classical "p" prefix (denoting "plasmid") and the abbreviation for the University of California, where early work on the plasmid series had been conducted. It is a circular double stranded DNA and has 2686 base pairs. pUC19 is one of the most widely used vector molecules as the recombinants, or the cells into which foreign DNA has been introduced, can be easily distinguished from the non-recombinants based on color differences of colonies on growth media. pUC18 is similar to pUC19, but the MCS region is reversed.
It has one ampR gene (ampicillin resistance gene), and an N-terminal fragment of β-galactosidase (lacZ) gene of E. coli. The multiple cloning site (MCS) region is split into the lacZ gene (codons 6–7 of lacZ are replaced by MCS), where various restriction sites for many restriction endonucleases are present. In addition to β-galactosidase, pUC19 also encodes for an enzyme called β-lactamase, which can degrade ampicillin and reduce its toxicity to the host.
The ori site, or origin of replication, is derived from the plasmid pMB1. pUC19 is small but has a high copy number. The high copy number is a result of the lack of the rop gene and a single point mutation in the ori of pMB1. The lacZ gene codes for β-galactosidase. The recognition sites for HindIII, SphI, PstI, SalI, XbaI, BamHI, SmaI, KpnI, SacI and EcoRI restriction enzymes have been derived from the vector M13mp19.
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