Molecular biology. A genotoxicological technique for measuring DNA damage in an individual cell using gel electrophoresis. Cell DNA fragments assume a formation as a comet with a tail on electrophoresis. The frequency of DNA-strand breaks depends on the length of the tail of the comet (tail length) and the amount of DNA in the tail. Tail moment is defined as the product of tail length and tail DNA content.
The alkaline comet assay (pH > 13) is commonly used to detect DNA single-strand breaks and double-strand breaks, alkali-labile sites and intermediates of DNA repair process.