Using a host cell to carry the vector allows for easy amplification and retrieval of specific clones from the library for analysis.
Researchers can choose a vector also considering the ideal insert size to find the desired number of clones necessary for full genome coverage.
[4][5] The first DNA-based genome ever fully sequenced was achieved by two-time Nobel Prize winner, Frederick Sanger, in 1977.
Sanger and his team of scientists created a library of the bacteriophage, phi X 174, for use in DNA sequencing.
[6] The importance of this success contributed to the ever-increasing demand for sequencing genomes to research gene therapy.
[7] These are due to the advance of genome-wide association studies from the ability to create and sequence genomic libraries.
For organisms with very small genomes (~10 kb), the digested fragments can be separated by gel electrophoresis.
Calculating the titer allows researchers to approximate how many infectious viral particles were successfully created in the library.
This allows researchers to also determine the percentage of infectious viral particles actually carrying a fragment of the library.
[11] A similar method can be used to titer genomic libraries made with non-viral vectors, such as plasmids and BACs.
By doing this test, researchers can also determine the efficiency of the ligation and make adjustments as needed to ensure they get the desired number of clones for the library.
[3] Below is a table of several kinds of vectors commonly used for genomic libraries and the insert size that each generally holds.
Many plasmids also carry a reporter gene that allows researchers to distinguish clones containing an insert from those that do not.
These particles are very efficient at infection and multiplication leading to a higher production of the recombinant λ chromosomes.
[3] However, due to the smaller insert size, libraries made with λ phage may require many clones for full genome coverage.
[14] Cosmid vectors are plasmids that contain a small region of bacteriophage λ DNA called the cos sequence.
[14] Bacterial artificial chromosomes (BACs) are circular DNA molecules, usually about 7kb in length, that are capable of holding inserts up to 300kb in size.
BAC vectors contain a replicon derived from E. coli F factor, which ensures they are maintained at one copy per cell.
[2] The figure to the right depicts a BAC vector being cut with a restriction enzyme, followed by the insertion of foreign DNA that is re-annealed by a ligase.
Furthermore, recombinant molecules should contain large enough inserts ensuring the library size is able to be handled conveniently.
The aforementioned genome-wide association studies can identify candidate genes stemming from many functional traits.
Genes can be isolated through genomic libraries and used on human cell lines or animal models to further research.
[17] Furthermore, creating high-fidelity clones with accurate genome representation and no stability issues would contribute well as intermediates for shotgun sequencing or the study of complete genes in functional analysis.
A high resolution map can be created by sequencing both ends of inserts from several clones in a genomic library.
[18][19] Genome-wide association studies are general applications to find specific gene targets and polymorphisms within the human race.
In fact, the International HapMap project was created through a partnership of scientists and agencies from several countries to catalog and utilize this data.
[20] Scientists from all of the participating nations are cataloging these attributes with data from populations of African, Asian, and European ancestry.
Such genome-wide assessments may lead to further diagnostic and drug therapies while also helping future teams focus on orchestrating therapeutics with genetic features in mind.
[20] For example, a research team has actually constructed a PAC shuttle vector that creates a library representing two-fold coverage of the human genome.
[21] Overall, advances in genome library construction and DNA sequencing has allowed for efficient discovery of different molecular targets.