Figure 1. Photographs of cells analyzed by comet assay analysis. This figure shows photographs taken from the comet assay analysis. Each spot represents the DNA of an individual cell. The “dark/white” round spot represents the intact DNA. Intact DNA is a large molecule that does not migrate much in the electrophoretic field. The less dark “comet shaped” area adjacent to the nucleus represents DNA breaks that are small enough to move in the gel. The arrow in A points toward a virtually intact cell whereas the arrow in B points toward a cell with a large “comet”, which is indicative of a large amount of DNA breaks.