Nucleic Acid Standards
Nucleic acid fragment size is usually reported in "nucleotides", "base pairs (bp)" or "kb” depending upon whether single- or double-stranded nucleic acid has been separated. Fragment size is usually determined by comparison with nucleic acid standards that contain fragments of known length.
Nucleic acid standards, also known as markers or ladders, are a set of standards that are used to identify the approximate size of a molecule run on a gel during electrophoresis, using the principle that molecular weight is inversely proportional to its mobility through a gel matrix.
Factors considered in selecting an appropriate ladder for a given sample include the type of ladder, fragment structure and conformation, the number of fragments and their separation patterns, and the suitability of the ladder and dyes to the gel respectively.
DNA Ladders
Amerigo Scientifc offers ideal DNA ladders for quantitative estimation of DNA mass in gels. OneMARK series is a ready-to-use format containing the fluorescent DNA stain and tracking dyes for direct loading onto unstained gels.
Benefits
- Versatile: size range from 50 bp to 10 Kb
- Consistency: sharp and clear bands for reliable results
- Convenient: optimized size ranges for analysis
The separation matrixes of nucleic acid electrophoresis include agar, agarose, polyacrylamide, and composite agarose-acrylamide gels. Among them, agarose and polyacrylamide are the two most used gels in nucleic acid electrophoresis. Polyacrylamide gels are suitable for separating nucleic acid molecules smaller than 1000 bp.
The easiest way to see the results of a gel electrophoresis experiment is to stain the gel with a nucleic acid stain. Ethidium bromide (EtBr) is a common stain in agarose and polyacrylamide gels. EtBr binds to DNA molecules by intercalating between adjacent base pairs and emits an intense red-orange fluorescence under UV light.
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