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The comet assay for DNA damage and repair

Principles, applications, and limitations

Molecular Biotechnology volume 26, Article number: 249 (2004) Cite this article

Abstract

The comet assay (single-cell gel electrophoresis) is a simple method for measuring deoxyribonucleic acid (DNA) strand breaks in eukaryotic cells. Cells embedded in agarose on a microscope slide are lysed with detergent and high salt to form nucleoids containing supercoiled loops of DNA linked to the nuclear matrix. Electrophoresis at high pH results in structures resembling comets, observed by fluorescence microscopy; the intensity of the comet tail relative to the head reflects the number of DNA breaks. The likely basis for this is that loops containing a break lose their supercoiling and become free to extend toward the anode. The assay has applications in testing novel chemicals for genotoxicity, monitoring environmental contamination with genotoxins, human biomonitoring and molecular epidemiology, and fundamental research in DNA damage and repair. The sensitivity and specificity of the assay are greatly enhanced if the nucleoids are incubated with bacterial repair endonucleases that recognize specific kinds of damage in the DNA and convert lesions to DNA breaks, increasing the amount of DNA in the comet tail. DNA repair can be monitored by incubating cells after treatment with damaging agent and measuring the damage remaining at intervals. Alternatively, the repair activity in a cell extract can be measured by incubating it with nucleoids containing specific damage.

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  1. Department of Nutrition, University of Oslo, PO Box 1046, Blindern, N-0316, Oslo, Norway

    Andrew R. Collins

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Correspondence to Andrew R. Collins.

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Collins, A.R. The comet assay for DNA damage and repair. Mol Biotechnol 26, 249 (2004). https://doi.org/10.1385/MB:26:3:249

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  • DOI: https://doi.org/10.1385/MB:26:3:249

Index Entries

  • Comet assay
  • single-cell gel electrophoresis
  • DNA damage
  • DNA repair
  • genotoxicity testing
  • molecular epidemiology