in Principles and process of Biotechnology by

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Following are the properties which make plasmids good cloning vectors:

i) Self-replicating: Plasmids contains origin of replication and hence they are able to multiply by themselves independently of the chromosomal DNA. They maintain their number in progenies.

ii) Low molecular weight: Plasmids have low molecular weight which makes them easy to handle and hence can be present in multiple copies.

iii) Multiple Cloning Sites: This is a site on plasmid which has recognition sites for many restriction enzymes.

iv) Selectable Marker:  Plasmid has certain genes which help in identifying the transformed cells. For example, antibiotic resistance genes.

v) High copy number: Due to low molecular weight of plasmids, they are present in multiple copies. High copy number plasmids are require to produce large quantities of the recombinant DNA.

vi) Host range: Plasmids used as coning vectors have narrow host range so that transmission of these plasmids to other organism in environment is avoided.

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