Gene library

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A gene library is a population of organisms, each of which carries a DNA molecule that was inserted into a cloning vector. Ideally, all of the cloned DNA molecules represent the entire genome of the organism. A gene library is also called gene bank. This term also represents the collection of all of the vector molecules, each carrying piece of the chromosomal DNA of the organism, prior to the insertion of these molecules into the population of the host cell.

[edit] Types of Gene Libraries

1. Plasmid libraries: Have a capacity of 10kb.
2. Phage libraries: Have a capacity of 23kb.
3. Cosmid libraries: Have a capacity of 45 kb.
4. Yeast artificial chromosome (YAC) libraries: Have a capacity of 1000kb.

[edit] Creating a library

The DNA molecules of an organism in interest are isolated. The DNA molecules are then partially digested by an endonuclease restriction enzyme. Sometimes, the DNA molecules are digested to different lengths of time in order to ensure that all the genes have been digested to manageable sizes. The digested DNA molecules are run on agarose electrophoresis for which a suitable range of lengths of DNA pieces are isolated and ligated to vector plasmids. Statistically, 99% of the genes will be incoporated into the plasmids. The plasmids then can be taken up by suitable hosts.The hosts are kept in liquid media and can be frozen at -80° C for a long time.Usually the hosts are bacteria that do not contain any plasmids so as to be sensitive to antibiotics.

The process of subdividing genomic DNA into clonable element and inserting them into host is called creating a library, a clone bank or a gene bank. A complete library of host cell will contain all of the genomic DNA of the source organism