*2.2.1 The vector system*

They are important cloning vehicles, within which the fragment of gene of interest is inserted and transferred into a suitable host system [11]. Mostly circular DNA that has small size and is of bacterial origin is utilized as vector. The vector should possess certain characteristics to make it suitable to be used for the process of genetic engineering:


In order to promote cloning within vector, it must possess certain important sites:

• **Ori site**—The process of replication initiates from this sequence. The presence of this site is necessary for independent replication of plasmid within the host cell. This sequence is also responsible for controlling the copy

number of the gene of interest. If a large number of copies of DNA of interest are required, it must be cloned in a vector containing ori site supporting high copy number.

