The Joining of DNA Molecules

The basic procedures of recombinant DNA techniques are (1) to join a DNA segment to a DNA molecule (known as vector) that can replicate, and (2) to provide an environment that allows reproduction of the joined DNA molecule.7 

Four types of vector can be used to clone fragments of foreign DNA and propagate them in Escherichia coll. They are plasmids, bacteriophage gamma, cosmids, and bacteriophage M13. All of these have the following properties necessary to be qualified as vectors  

They have ability to replicate autonomously in E. coll. 

They contain a selection marker for the easy separation and purification of the vector from bacterial nucleic acids. 

They have regions of DNA that are not essential for propagation in bacteria, so that foreign DNA can be inserted into these regions. 

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DNA ligase—Protein that facilitates the joining of DNA molecules. 

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