pBR322, which is frequently used as a vector for cloning gene in E. coli is a/an
(a) original bacterial plasmid
(b) modified bacterial plasmid
(c) viral genome
E. coli plasmid pBR322 is the most versatile and widely used cloning vector, it contains both ampicillin and tetracyclin-resistance genes and a number of unique restriction enzyme cleavage sites.