6.3 Cloning vectors
For the cloning of any molecule of DNA it is necessary for that DNA to be incorporated
into a cloning vector. These are DNA elements that may be stably maintained and
propagated in a host organism for whichthe vector has replication functions. A typical
host organism is a bacterium such asE. coliwhich grows and divides rapidly. Thus any
vector with a replication origin inE. coliwill replicate (together with any incorporated
DNA) efficiently. Thus, any DNA cloned into a vector will enable the amplification of the
inserted foreign DNA fragment and also allow anysubsequent analysis tobe undertaken.
In this way the cloning process resembles the PCR although there are some major
differences between the two techniques. By cloning, it is possible to not only store a copy
of any particular fragment of DNA, but also produce unlimited amounts of it (Fig. 6.10).
The vectors used for cloning vary in their complexity, their ease of manipulation,
their selection and the amount of DNA sequence they can accommodate (the insert
Stable gene bank (gene library),
each vector containing
a different foreign DNA fragment
Isolation of one clone from
library by gene library screening
Amplify single clone
from gene library for
further analysis
Fig. 6.10Production of multiple copies of a single clone from a stable gene bank or library.
206 Recombinant DNA and genetic analysis
