title: A novel combined method for cost-benefit production of DNA ladders.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  The highest advantage of this cost-benefit approach is to produce different types of molecular weight markers by using an effective and short protocol.
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Saied
authors.initials: S
authors.lastname: Mostaan
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Ajorloo
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran ; Department of Anatomical Sciences and Genetics, Isfahan Medicine School, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Khanahmad
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Reza Ahangari
authors.initials: RA
authors.lastname: Cohan
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Zahra Rikhtegaran
authors.initials: ZR
authors.lastname: Tehrani
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Rezaei
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Fateme
authors.initials: F
authors.lastname: Fazeli
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Behdani
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Sakineh Karimi
authors.initials: SK
authors.lastname: Zare
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Zeinab
authors.initials: Z
authors.lastname: Karimi
authors.affiliation: Department of Virology, Faculty of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Seyed Hamid Reza
authors.initials: SH
authors.lastname: Mozhgani
authors.affiliation: Department of R and D, Institute Pasteur of Iran, Tehran, Iran.
authors.forename: Rasul
authors.initials: R
authors.lastname: Moukhah
keywords: DNA ladder; DNA marker; molecular weight