Related Experiment Video
Updated: Jun 13, 2026

Agarose Gel Electrophoresis for the Separation of DNA Fragments
Published on: April 20, 2012
Simple and practical staining of DNA with GelRed in agarose gel electrophoresis
Qing Huang1, Larry Baum, Wei-Ling Fu
1Department of Laboratory Medicine, Southwest Hospital, Third Military Medical University, Chongqing, China.
Background:
Although SYBR Gold or SYBR Green I have been used in the loading buffer as a DNA stain safer than ethidium bromide for agarose gel electrophoresis, electrophoretic mobility of DNA is altered and thus DNA fragment size cannot be accurately determined.
Methods:
A method using GelRed in the loading buffer was developed to stain DNA fragments in agarose gel electrophoresis.
Results:
Among various concentrations of GelRed, SYBR Gold, or SYBR Green I tested in the loading buffer, only the highest tested concentration of GelRed, i.e., 100x GelRed, did not change band mobility. Evaluations using various sizes of PCR products at different concentrations further confirmed that 100x GelRed could be used to accurately determine DNA fragment size. The reagent can be stored at 4 degrees C for at least 1 year without a decrease in staining sensitivity.
Conclusions:
The 100x GelRed is a sensitive and safe alternative to ethidium bromide and better than either SYBR Gold or SYBR Green I for size determination in agarose gel electrophoresis. Our laboratory now uses the GelRed method routinely with great consistency and success.
Related Concept Videos
DNA Agarose Gel Electrophoresis
Gel extraction follows five major steps: running gel electrophoresis to separate fragments, isolating the individual bands, extracting DNA from those bands, and removing the dye and salts from the extracted mixture to obtain pure DNA.
In cloning experiments, both the insert and vector DNA...
Southern Blot
Denatured DNA fragments must be transferred onto a carrier membrane from the gel to make it accessible to a probe - a small ssDNA fragment complementary to the target DNA...
Two-dimensional Gel Electrophoresis
The first dimension separation uses the isoelectric focusing or IEF technique performed on immobilized pH gradient (IPG) strips that separate proteins according to their isoelectric points.
Biological samples, such as cells...
Simple Staining Technique
DNA Isolation
SDS-PAGE
A variation of gel electrophoresis, termed polyacrylamide gel electrophoresis (PAGE), is commonly used for separating proteins according to their molecular size by passing them through a polyacrylamide gel. Because of the varying charges associated with amino acid side chains, PAGE can be used to separate intact proteins...

