Patent ID: 7445910

Claim:
A method for the enumeration of mammalian cell micronuclei, while distinguishing micronuclei from the chromatin of dead and dying cells, the method comprising: contacting a sample containing mammalian cells with a first fluorescent DNA dye that permeates dead and dying cells but not viable cells, that covalently binds chromatin, and that has a fluorescence emission spectrum; contacting the sample with one or more lysis solutions that result in digestion of mammalian cell outer membranes but retention of nuclear membranes, thereby forming free nuclei and/or micronuclei; contacting the free nuclei and/or micronuclei with RNase to substantially degrade RNA; staining cellular DNA with a second fluorescent DNA dye having a fluorescent emission spectrum that does not substantially overlap with the fluorescent emission spectrum of the first fluorescent DNA dye; exciting the first and second fluorescent DNA dyes with light of appropriate excitation wavelength; and detecting the fluorescent emission and light scatter produced by the nuclei and/or micronuclei, while excluding chromatin from the dead and dying cells, and counting the number of micronuclei in said sample relative to the number of nuclei.