Construction of a synthetic vector for preparation of a 100 base pair DNA ladder

DNA size markers are widely used to estimate the size of DNA samples on agarose or polyacrylamide gel electrophoresis (PAGE). DNA markers can be prepared by mixing PCR products with definite sizes. Alternatively, they are prepared by restriction enzyme digestion of the genomic DNA of bacteriophages or natural and synthetic DNA plasmids. The present study describes engineering of a synthetic plasmid which produces a 100 bp DNA ladder, a popular DNA size marker, upon digestion with a single restriction enzyme. Our strategy consisted on sequential cloning of ten PCR products of 100 to 1000 bp in plasmid pTZ57R, using the BamHI and BglII restriction enzymes and releasing the fragments from the recombinant plasmid by enzyme EcoRV. This strategy could be applied to construct various complex synthetic vectors to produce different DNA ladders.