What is Comet Assay ?

The comet assay, also called the 'Single Cell Gel Assay', is the technique to  detect  DNA damage and repair at the level of single cells. This is one of the advanced technique in the oncology. This technique was developed by Swedish researchers  Östling & Johansson in 1984. This technique was later modified by N.P. Singh et al., in 1988 as Alkaline Comet Assay.
'Comet Assay' is one of the most popular  tests of DNA damage detection  (e.g., single- and double-strand breaks, oxidative-induced base damage, and DNA-DNA/DNA-protein cross linking ) by electrophoresis, developed in recent years.

Merits Of Comet Assay :

• Very high sensitivity to detect DNA damage
• Rapid and easy to handle
• Little  amount of cell samples needed
• Applied to most eukaryotic cells

Methodology :

Comet Assay involves the following steps :
1.  Slide preparation : Mixing of cells with low melting agarose, and spread over glass microscope slides
2.  Lysis:  lysis of  cell membrane and other proteins
3.  Unwinding of DNA
4.  Electrophoresis
5.  Neutralization
6.  Staining and scoring

Applications :

• Genotoxicity Studies
• DNA Repair
• Apoptosis
• Visual quantification of DNA double strand breaks in bacteria
• Free Radical Biology
• Nutritional Toxicology
• Biomonitoring
• Clinical Applications
• Cell cycle analysis

Reviews :

• McKelvey-Martin, V.J., M.H.L. Green, P. Schmezer, B.L. Pool-Zobel, M.P. De MJo, and A. Collins.  The single cell gel electrophoresis assay (comet assay):  A European review.  Mutat. Res. 288: 47-63

• Tice, R.R.  The single cell gel/comet assay:  a microgel electrophoretic technique for the detection of DNA damage and repair in individual cells.  In:  Environmental Mutagenesis (D.H. Phillips and S. Venitt, eds.), Bios Scientific Publishers, Oxford, 315-339.
  

• Fairbairn, D.W., P. L. Olive, and K.L. O'Neill.  The Comet assay:  a comprehensive review.  Mutat. Res. 339: 37-59.
  

• Anderson D., T-W. Yu, and D.B. McGregor. Comet assay responses as indicators of carcinogen exposure. Mutagenesis 13: 539-555.
  

• Rojas, E., M.C. Lopez, and M. Valverde.  Single cell gel electrophoresis.  Methodology and applications.  J. Chromat. B 1-2: 225-254.
  

• Tice RR, Agurell E, Anderson D, Burlinson B, Hartmann A, Kobayashi H, Miyamae Y, Rojas E, Ryu JC, Sasaki YF. Single cell gel/comet assay: guidelines for in vitro and in vivo genetic toxicology testing. Environ Mol Mutagen 2000;35(3):206-21.
  

Comet-FISH :

• Comet assay interest group homepage
• Comet assay mailing list
• comet-assay
• Apoptosis Interest Group
• DNA Repair Interest Group
• Public domain image analysis for comet assay
• Perceptive software
• Kinetic Images software 
• LAI Comet Assay Analysis System