Methodological design. Micronuclei formation was induced by incubation in 0.05 μg/ml demecolcine for 46 h followed by 2 mg/ml mitomycin for 2 h. Cells were then treated with 10 μg/ml cytochalasin B for 1 h. MII oocytes were mechanically enucleated and injected with one somatic micronucleus, which were previously exposed or not to pCX-EGFP. After 2 h, oocytes and reconstituted embryos were chemically activated. After 48 h of IVC, cleavage stage was assessed. Moreover, the DNA from some embryos was stained with DAPI for evaluation of nuclear replication and others were karyotyped. At day 4 of IVC, egfp expression was evaluated.