pBR327 vectors are derived from pBR322, by deletion of nucleotides between
1427 to 2516. These nucleotides are deleted to reduce the size of vector and eliminate sequences that were known to interfere with the expression of the cloned DNA in eukaryotic cells. It contains genes for resistance against two antibiotics (tetracycline and ampicillin). Both pBR322 and pBR327 are very commonly used plasmid vector in molecular biology.