Abstract:

BACKGROUND: DNA molecular weight standard (DNA Ladder) is one of necessary reagents in molecular biological laboratory. It can correctly measure the length of DNA fragments and serve as the DNA molecular weight standard. Now, there are two methods to prepare the DNA Ladder, one is PCR technique, the other is through DNA digestion by restriction enzyme. The two methods all have some merits and drawbacks. The first one can produce standard bands, but is difficult to obtain large bands. The second method is to prepare DNA Ladder restriction digestion of plasmid or phage DNA. In previous study, we have amplified 100-500 bp DNA fragments by using PCR technique, then purified the PCR product and prepared DNA Ladder. The bands of the prepared DNA Ladder were clear, higher definition and could be equal with that of commercial products. It could be used in the molecular biology experiments. 
OBJECTIVE: To prepare DNA molecular weight standard control.
METHODS: A specific plasmid pUC-DNA for PCR amplification was constructed, according to the sequence of pUC-DNA. Primers were designed to amplify 100-1 000 bp DNA fragments followed by primer5.0. 100-1 000 b p series DNA fragments were amplified and electrophoresised in 2% agarose gels. After identification by PCR recovery products and DNA sequencing, the DNA sequences were analyzed according to the pUC-DNA and the homology analysis was compared analyzed by blast. The PCR products were extracted by phenol/chloroform, precipitated with ethanol and mixed them proportionally.
RESULTS AND CONCLUSION: 100-1 000 bp DNA fragments were successfully amplified by PCR technique, and the size of the bands were the same as the expected. The purified bands were clear. The 100-1000 bp DNA ladder was prepared in our laboratory. The method is convenient and the size of the prepared DNA ladder is standard, it could be used in the molecular biology experiments.