Question: what are the essential features of a cloning vector?
Answer: Replication. Replication of plasmid DNA is carried by the same enzymes that replicate the E. ... 
Selectable Markers (Antibiotic resistance) ... 
Multiple cloning sites (or polylinkers) ... 
Single-stranded DNA production. ... 
Bacteriophage promoters. ... 
Miniature Preparation of Bacterial Plasmid.