|Index to this page| Recombinant DNA is DNA that has been
created artificially. DNA from two or more sources is
incorporated into a single recombinant molecule. 5' GGATCC 3' 3'
CCTAGG 5' To be useful, the recombinant molecule must be
replicated many times to provide material for analysis,
sequencing, etc. Producing many identical copies of the same
recombinant molecule is called cloning. Cloning can be done in
vitro, by a process called the polymerase chain reaction (PCR).
Here, however, we shall examine how cloning is done in
vivo.Cloning in vivo can be done in In every case, the
recombinant DNA must be taken up by the cell in a form in which
it can be replicated and expressed. This is achieved by
incorporating the DNA in a vector. A number of viruses (both
bacterial and of mammalian cells) can serve as vectors. But here
let us examine an example of cloning using E. coli as the host
and a plasmid as the vector. |Electron micrograph showing
plasmids (21K)| Plasmids are replicated by the same machinery
that re