A
genomic library is a collection of the total genomic
DNA from a single
organism. The DNA is stored in a population of identical
vectors, each containing a different
insert of DNA. In order to construct a genomic library, the organism's DNA is
extracted from
cells and then digested with a
restriction enzyme to cut the DNA into fragments of a specific size. The fragments are then inserted into the vector using
DNA ligase. Next, the vector DNA can be taken up by a host organism - commonly a population of
Escherichia coli or
yeast - with each cell containing only one vector molecule. Using a host cell to carry the vector allows for easy amplification and retrieval of specific
clones from the
library for analysis.