Gene Libraries
June 1st, 2008 | by admin |One exceptional application of these techniques has been the construction of gene libraries. A gene library contains the entire complement of DNA (and therefore genes) from an organism in the form of DNA fragments inserted into recombinant plasmids or phages. DNA containing an organism’s genes (i.e., genomic DNA) can be isolated from a cell or tissue of interest, including human tissue, and cut into pieces of manageable size using a restriction endonuclease. These DNA fragments, several million of them and all of different lengths, can be cloned into bacterial plasmids or phages, as described above, so that each vector carries exactly one genomic DNA fragment.
The recombinant vectors are then re-introduced into the bacteria, which can be plated onto agar plates and grown into individual bacterial colonies or phage plaques (areas of bacteria infected with phages). Now each bacterial colony, or each phage plaque, houses a recombinant plasmid bearing a different inserted fragment of DNA derived from the genomic DNA of the original cell or tissue. Each colony or plaque represents a different DNA “clone.” Specific clones containing specific genes can be identified on the basis of their nucleotide sequences16,17 (see below), expanded
into large-scale cultures, and their recombinant DNA isolated. In this way, new genes are cloned.
