Genomic library

     A genomic library is a collection of bacterial or bacteriophage clones, each containing at least one copy of every DNA sequence in a genome of an organism. In a single library, the entire genome of an organism is represented as a set of DNA fragments inserted into a vector molecule.

Construction of a genomic library

      To construct a genomic library, the genomic DNA of the organism is extracted and is fragmented by a restriction enzyme. The vector is also isolated from a host bacterium and cut with the same restriction enzyme used for the digestion of the genomic DNA. The linearized vector molecule is inoculated with the fragments of genomic DNA along with DNA ligase so that each of the genomic DNA fragments is inserted into each vector molecule resulting in a recombinant DNA molecule. Each of the recombinant vector molecules will have different fragments of genomic DNA and all these recombinant DNA molecules are introduced into a suitable host organism such as bacterial cells or phage particles.

Locating gene of interest from DNA libraries

    A DNA probe is a small, fluorescently or radioactively labeled DNA molecule that is used to locate similar or complementary sequences among a long stretch of DNA molecule or bacterial colonies such as genomic or cDNA libraries or in a genome. Since the probe is labeled with a fluorescent dye or radioactive isotopes of phosphorus, it's binding to specific sequences can be detected.