Introduction
DNA damage, due to environmental factors and normal metabolic processes inside the cell, occurs at a
rate of 1,000 to 1,000,000 molecular lesions per cell per day. While this counts for only a small part of
the human genome's approximately 6 billion bases (3 billion base pairs), unrepaired lesions to critical
genes can impede a cell's ability to carry out its function and appreciably increase the likelihood of
cancer.
The comet assay, or single cell gel electrophoresis assay (SCGE), is a common technique for
measurement of DNA damage in individual cells. Under an electrophoretic field, damaged cellular
DNA (containing fragments and strand breaks) is separated from intact DNA, yielding a classic “comet
tail” shape under the microscope. Extent of DNA damage is usually visually estimated by comet tail
measurement; however, image analysis software is also available for measuring various parameters.
The OxiSelect™ Comet Assay is a fast and sensitive kit for the measurement of cellular DNA damage.
Each kit provides sufficient reagents to perform up to 75 assays.
Assay Principle
The Cell Biolabs OxiSelect™ Comet Assay is a single cell gel electrophoresis assay (SCGE) for simple
evaluation of cellular DNA damage. First, individual cells are mixed with molten agarose before
application to the OxiSelect™ Comet Slide. These embedded cells are then treated with a lysis buffer
and alkaline solution, which relaxes and denatures the DNA. Finally, the samples are electrophoresed
in a horizontal chamber to separate intact DNA from damaged fragments. Following electrophoresis,
the samples are dried, stained with a DNA dye, and visualized by epifluorescence microscopy. Under
these conditions, the damaged DNA (containing cleavage and strand breaks) will migrate further than
intact DNA and produce a “comet tail” shape (see Figure 1). Each kit provides sufficient reagents to
perform up to 75 assays.