Cloning and Expression Vectors

Cloning and Expression Vectors - In recent years, techniques for manipulating prokaryotic as well as eukaryotic DNA have witnessed a remarkable development. This has allowed breakage of a DNA molecule at two desired places to isolate a specific DNA segment and then insert it in another DNA molecule at a desired position.

The product thus obtained, is called recombinant DNA and the technique often called genetic engineering. Using, this technique we can isolate and clone single copy of a gene or a DNA segment into an indefinite number of copies, all identical.

This became possible because vectors like plasmids and phages reproduce in a host (e.g. E. coli) in their usual manner even after insertion of foreign DNA, so that the inserted DNA will also replicate faithfully with the parent DNA. This technique is called gene cloning.

With this technique, genes can be isolated, cloned and characterized, so that the technique has led to significant progress in all areas of molecular biology. A variety of vectors have been developed which not only allow multiplication, but' may also be manipulated in such a way that the inserted gene may express in the host.

Due to the importance of a variety of these cloning and expression vectors in genetic engineering experiments, they are discussed in some detail in this chapter. The techniques used for inserting foreign DNA in these vectors and the development of chimeric DNA molecules (for developing molecular probes, gene libraries, etc.).