Final answer:
Plasmid cloning vectors require an origin of replication, a selectable marker, and a multiple cloning site (MCS) for effective cloning.
Step-by-step explanation:
Plasmid cloning vectors must include several key features to ensure efficient cloning. Primarily, a plasmid vector should have an origin of replication which allows the plasmid to replicate independently within a bacterial cell. Additionally, the presence of a selectable marker, such as an antibiotic resistance gene, is crucial for identifying and selecting cells that have successfully taken up the plasmid. Finally, a plasmid vector should contain a multiple cloning site (MCS), which is a sequence with multiple unique restriction enzyme recognition sites that allow for the insertion of foreign DNA fragments after enzymatic digestion.