Method for enumeration of mammalian cell micronuclei

A method for the enumeration of mammalian cell micronuclei, while distinguishing micronuclei from the chromatin of dead and dying cells, the method comprising:

• exposing a mammalian cell sample comprising viable cells and dead and dying cells to (i) first and second fluorescent DNA dyes that are characterized by fluorescent emission spectra that do not substantially overlap, and (ii) a lysis solution that lyses cellular membranes but retains nuclear membranes, said exposing being carried out under conditions effective to allow the first fluorescent DNA dye to label chromatin of dead and dying cells but not viable cells and the second DNA dye to label nuclei and/or micronuclei from all cells;
• exciting the first and second fluorescent DNA dyes;
• and
• detecting and distinguishing fluorescent emission and light scatter produced by the nuclei and/or micronuclei while excluding fluorescent emission by the chromatin of dead and dying cells.