Genomic DNA Libraries, Construction and Applications

Abstract

By virtue of the powerful technology developed in molecular biology, it is possible to isolate any DNA fragment in the genome of an organism and, after reverse transcription, any transcribed gene in the form of a complementary DNA. The isolation (cloning) procedure involves the insertion of the DNA fragment into a vector, capable of replication in a microorganism, which allows production of large quantities of the DNA fragment for physical or biological analysis. Upon determination of the location in the genome from which the particular DNA fragment was derived, that fragment acquires the property of a DNA marker. Such DNA markers are a prerequisite for physical and genetic mapping of the genome of the organism. DNA markers are also of importance for the diagnosis of genetic diseases. DNA markers can be divided into several different classes depending on the way in which the markers were selected among the fragments of genomic DNA. Examples of such classes are anonymous, micro- and minisatellites, restriction fragment length polymorphism (RFLP) markers, and NotI linking clones. Vectors and clone libraries of different types can be used to clone markers. Lambda-based vectors and genomic libraries of different kinds are commonly used for this purpose. Many different variants of λ-based vectors that combine features of different cloning vehicles (plasmids, M13 and P1 phages) have been created for this purpose. The use of each vector is usually limited to a specific task: the construction of general genomic libraries (which contain all genomic DNA fragments) or special genomic libraries (which contain only a particular subset of genomic DNA fragments). Among these special libraries, NotI linking and jumping libraries have particular value for physical/genetic mapping and sequencing of the human genome. Shotgun and slalom libraries are usually used for sequencing purpose and comparative genomics. Keywords: Blue–white Selection; Genetic Selection; Polylinker; Restriction Enzyme; (STS) Sequence-tagged Site