pBR322 is one of the standard cloning vectors obtained from E. coli. p stands for plasmid, BR stands for Boliver and Rodriguez and 322 is the order in which it was developed in the lab. It is genetically engineered and contains two antibiotic resistance genes for ampicillin and tetracycline, an origin of replication (ori), unique restriction sites for many restriction enzymes and a rop gene, which codes for proteins that are involved in regulating the copy number of plasmid inside the host cell.