The Comet-FISH technique combines the Comet Assay (single-cell gel electrophoresis) with Fluorescent In Situ Hybridization (FISH) to create a tool for the detection of overall and region-specific DNA damage and repair in individual cells. Comet allows separation of fragmented from non-fragmented DNA and quantification of DNA damage and repair. FISH tags specific DNA sequences of interest. Used together, you can identify whether your gene of interest falls within the damaged or undamaged region of DNA within a particular cell. Comet-FISH has been used to detect site-specific breaks in DNA regions that are relevant for development of various diseases, and to study the distribution of DNA damage and repair in the complete genome. Detection via Comet-FISH has also provided insights into mechanisms of cancer development and chemoprevention.

In the May issue of Cold Spring Harbor Protocols, Michael Glei and colleagues from Friedrich-Schiller-University Jena provide Comet Fluorescence In Situ Hybridization (Comet-FISH): Detection of DNA Damage, a set of detailed instructions for performing the Comet-FISH assay.