ABSTRACT
Identification of the cells that contain the DNA fragment of interest allows the purification of large amounts of that single recombinant DNA and hence the foreign DNA fragment. Consider an experimental goal which is to make large amounts of a particular DNA fragment in pure form from a mixture of DNA fragments. There are a wide variety of different procedures for cloning DNA into either plasmid or viral vectors but the basic scheme of events is often the same. A DNA library is a collection of cloned DNA fragments in a cloning vector that can be searched for a DNA of interest. If the goal is to isolate particular gene sequences, two types of library are useful: Genomic DNA libraries and cDNA libraries. Genomic libraries are screened by hybridization with a DNA probe that is complementary to part of the nucleotide sequence of the desired gene.
