Gene Cloning

The discovery of two naturally occurring biological molecules, plasmid DNA and restriction enzymes, with remarkable properties have made possible the development of methods to isolate and manipulate specific DNA fragments. Through this technology, a DNA fragment, even an entire gene and its controlling elements, can be isolated and rejoined with a plasmid or phage DNA, and the hybrid DNA molecule can be inserted into a bacterium. The foreign DNA insert can be multiplied inside the bacterial host and induced to express or synthesize the protein product of the foreign DNA. The entire process through which this can be achieved is called recombinant DNA technology or genetic engineering. The recombinant DNA technology has been extended to animal and plant cells. In this chapter, methods for isolation, modification, rejoining and replication of genomic DNA, and production of new or enhanced protein products within a host cell have been described.