Plasmid pUC18
A plasmid is a circular dsDNA molecule a few hundred or
thousand base pairs in circumference. Naturally-occurring plasmids
are viruses of bacteria. The artificial plasmid pUC18 has been
genetically engineered to include (1) a gene for antibiotic
resistance to Ampicillin (ampR), and (2)
a gene (and its promoter)
for the enzyme beta-galactosidase
(lacZ). The lacZ gene contains a (3)
polylinker region, with a
series of unique restriction sites found nowhere else in the
plasmid. Digestion with any one of these endonucleases will make a
single cut that linearizes the circular plasmid DNA, and allow it to recombine
with foreign DNA that has been cut with the same
endonuclease.
Figures © 2002 by Griffiths et al.;
all text material © 2014 by Steven M. Carr