AAT Bioquest

What methods are currently used to quantify DNA?

Posted February 4, 2020


DNA concentration in a sample can be determined in several ways:

Absorbance – DNA concentration is calculated by measuring the absorbance at 260 nm, and the turbidity at 320 nm, by using the following formula:

Concentration (µg/mL) = (A260 reading – A320 reading) × dilution factor × 50 µg/mL

Fluorescence – a method requiring a fluorescent DNA binding dye, a fluorometer that detects fluorescent dyes, and DNA standards to generate a standard curve. This method is more sensitive than the absorbance method and may be used for samples with low-concentration

Agarose Gel Electrophoresis – a method that requires horizontal gel electrophoresis tank, analytical-grade agarose, running buffer, intercalating DNA dye, and an appropriately sized DNA standard. The isolated DNA sample is loaded into a well of agarose gel alongside the standard. As the electric current flows, DNA migrates towards the anode, separating the DNA fragments by size as smaller DNA fragments travel faster than larger ones. The DNA in the gel can be visualized by an intercalating dye such as Cyber Green™ or Cyber Orange™ and then DNA can be quantified by comparing the sample with the standard.

Additional resources

Cyber Green™ Nucleic Acid Gel Stain [Equivalent to SYBR® Green]

Cyber Orange™ Nucleic Acid Gel Stain