pBR322 and pBR327 Vectors, Cloning Vector, Plasmid Vector, Ampicillin, Tetracycline

	pBR322 and pBR327 Vectors - The naturally occurring plasmids may not possess all the above and other essential properties of a suitable cloning vector. Therefore, one may have to restructure them by inserting genes of relaxed replication and genes for antibiotic resistance. This has actually been done and suitable plasmid vectors have been obtained. One of the standard cloning vectors widely used in gene cloning experiments is pBR322 (derived from E. coli plasmid ColE1), which is 4,362 bp DNA and was derived by several alterations in earlier cloning vectors (pBR322 was named after Bolivar and Rodriguez, who prepared this vector).
It has genes for resistance I against two antibiotics (tetracycline and ampicillin), an origin of replication and a variety of restriction sites for cloning of restriction fragments obtained through cleavage with a specific restriction enzyme. Another vector pBR327 was derived from pBR322, by deletion of nucleotides between 1,427 to 2,516. These nucleotides are deleted to reduce the size of the vector and to eliminate sequences that were known to interfere with the expression of the cloned DNA in eukaryotic cells. pBR327 still contains genes for resistance against two antibiotics (tetracycline and ampicillin). Both pBR322 and pBR327 are very common plasmid vectors.