The desirable characteristics in plasmids to function as effective cloning vector are: • They should have unique cleavage sites for several restriction endonucleases which could be used as cloning sites. • The replication origin of the plasmid should be compatible with the host for which it is designed • Presence of marker genes in the plasmid (such as antibiotic resistant) so that cells that are transferred with the plasmid can be easily selected.