Answer:
A plasmid is a small circular extra chromosomal DNA found in the bacteria. It can replicate independently. It was first introduced by the Lederberg in 1952. The main characteristics of the plasmid that are required to clone a DNA are its origin of replication, cloning site, and a selectable marker.
The bacterial plasmid should have high copy number and multiple origin of replication in order to replicate the DNA fastly. Cloning site is the site where the gene of interest is introduced in order to make multiple copies of DNA. The selectable marker is important in order to distinguish transformed cell from non- transformed cell.