Many replacement vectors (e.g., the EMBL series, {lambda}2001, and {lambda}DASH) contain a series of restriction sites, arranged in opposite orientations, at each end of the central stuffer fragment. Digestion of these vectors with two different restriction enzymes yields left and right arms, a stuffer fragment, and short segments of the polycloning sites. These can easily be removed from the arms by differential precipitation with isopropanol or spun-column chromatography.
