Comet-Assay

The comet assay (also called Einzelzellgelelektrophorese ) is a technique of gel electrophoresis, by which it is possible to determine DNA damage in individual cells. Was developed in 1984 by the assay Östling and Johanson for detecting DNA double-strand breaks. With the advancement by Singh in 1988 could be detected by the use of basic buffers in addition to DNA single-strand breaks.

The principle of the Comet assay relies on cells that lysed, embedded in agarose and subjected to an electric field, the so-called electrophoresis. During electrophoresis, the negatively charged DNA migrates to the positive terminal and thanks to the pores in the agarose, the fragments separated on the size according as the smaller fragments in a certain time a further distance to travel than the larger ones. However, chromosomal DNA is too large to migrate as a whole, in the electric field. Only damaged, fragmented DNA is here able to migrate out of the nucleus. Under the microscope, the UV damaged cells, which were previously stained with fluorescent dyes such as ethidium bromide now appear, with a tail of DNA fragments, which gives them the appearance of a comet.

The Comet assay, all cells may be used, which have a cell nucleus.

The implementation of the Comet assay is relatively simple and fast. Evaluates the number of damaged and undamaged nuclei, either by hand or by special computer programs with visual observation.