(a) ori: It is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. It is also responsible for controlling the copy number of the linked DNA.
(b) amp R : The ligation of alien DNA is carried out at a restriction site present in any antibiotic resistance gene.
(c) rop: It codes for the proteins involved in the replication of the plasmid.
