Biology Reference
In-Depth Information
Figure 6.1
Generalized scheme outlining the steps used in cloning DNA in
E. coli
. There are four
major components: obtaining DNA fragments, joining them to the vector, introducing the recom-
binant molecule into an appropriate host cell, and identifying or selecting the recombinant DNA of
interest. All of these steps can be achieved in several ways. Choosing an appropriate cloning scheme
depends upon the goals of the experiment. (Revised from Old and Primrose 1989.)
polymerase chain reaction ([PCR], described in Chapter 8) makes the construc-
tion of libraries less important than formerly, especially if the goal is to isolate
only one or a few genes. However, complete libraries are essential if the entire
genome is to be sequenced. References at the end of this chapter provide addi-
tional information and protocols on constructing libraries.
6.3 The Perfect Genomic Library
No library is perfect. However, a perfect
genomic library
would contain all of
the DNA sequences in the entire genome. The library would be stable and have
a manageable number of overlapping clones. The clones would contain suffi-
ciently large DNA segments that they could contain whole genes and their
