Molecular genetics. A standardized technique for
assessing DNA damage caused by genotoxic agents in cycling cells. Micronuclei originate from chromosome fragments or whole chromosomes that fail to engage with the mitotic spindle and therefore lag behind when the cell divides. After the first cell cycle including genotoxic treatment and induction of chromosome aberrations, the cells are incubated with cytochalasin B which blocks cytokinesis, but not karyokinesis. The amount of binucleated cells with micronuclei is a measure of the DNA damage.