Fig. 2. The three main roads to tetraploidy. Cell-cell fusion and failure of cytokinesis generate binucleated cells that contain two centrosomes. Binucleated cells can form mononucleated tetraploids after successful passage through the next mitosis. Mitotic slippage is a cellular adaptation to persistent mitotic arrest. Cells bypass anaphase, telophase and cytokinesis, and progress into the next G1 phase without correcting the mitotic error that triggered the arrest. Cells that are derived from mitotic slippage contain a single tetraploid nucleus that is accompanied by two centrosomes. 2N, diploid nucleus; 4N, tetraploid nucleus; 4C, diploid nucleus with replicated chromosomes.