DNA ladders also known as DNA molecular weight markers are among the most commonly used reagents in molecular biology research. DNA ladders function as molecular rulers, allowing one to determine the size of DNA fragments.
We have constructed two plasmids that produce 1 kb or 100 bp DNA ladders when digested with the EcoRV or the PstI restriction enzyme, respectively. Unlike many currently available DNA ladders, the 100 bp ladders migrate appropriately on both agarose and polyacrylamide gels. 100 ml of E. coli cultures for each of the two plasmids is sufficient to prepare 100 bp or 1 kb DNA ladders for 1 000 lanes. The plasmids allow the production of DNA ladders at less than a penny a lane, a fraction of the cost of using commercial DNA ladders.
The plasmids to produce the Penn State DNA ladders are available without licensing restrictions to nonprofit academic users through the Addgene plasmid repository:
pPSU1 plasmid at Addgene
pPSU2 plasmid at Addgene
Instructions for preparing the Penn State DNA ladders from the plasmids.
Penn State News article about the project.
This project was driven by undergraduates in the laboratory.
We are grateful for funding support from:
Penn State (Eberly College of Science Undergraduate Research Support) and
NIH National Institute of General Medical Sciences.
Henrici, R.C., Pecen, T.J., Johnston, J.L and Tan, S. (2017) The pPSU plasmids for generating DNA molecular weight markers, Scientific Reports, 7:2438.