A novel combined method for cost-benefit production of DNA ladders

Molecular deoxyribonucleic acid markers are one of the most important tools in molecular biology labs. The size of DNA molecule is determined by comparing them with known bands of markers during gel electrophoresis. In this study, we have suggested an efficient strategy to produce molecular weight markers in an industrial scale.

A combination of two previously known methods, restriction enzyme digestion and polymerase chain reaction (PCR), was used. The enzymatic digestion process was based on designing and constructing plasmids which equaled in size with the bands of ladder and produce the DNA fragment by plasmid linearization through digestion. In the PCR method, the DNA fragments with length 102 bp lesser than the related bands in DNA ladder are amplified by PCR and cloned in pTZ57T/A cloning vector. Then, PCRs with forward and reverse 100-bp primers on the resulting plasmids amplify the ladder fragments. F100 and R100 primers bind to the backbone of pTZ57R (without insert) and amplify a 100-bp PCR product. PCR on the plasmid with insert amplifies DNA fragment with 102+ insert length bp size.

Upon application of this strategy, 2000-10,000 bp DNA fragments were produced by enzymatic digestion of plasmids of the same size. Moreover, 100-1500 bp fragments were produced during PCR using only a set of forward and reverse (100 bp) primers.

The highest advantage of this cost-benefit approach is to produce different types of molecular weight markers by using an effective and short protocol.