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. Author manuscript; available in PMC: 2016 Jun 1.
Published in final edited form as: Trends Genet. 2015 Apr 25;31(6):307–315. doi: 10.1016/j.tig.2015.03.011

Figure 1.

Figure 1

Cell Cycle Variants Yielding Polyploid Cells. (A) The archetypal cell cycle responsible for cell proliferation contains a G1 phase during which sufficient cell growth must occur prior to the onset of DNA replication in S phase. Another gap phase (G2) precedes mitosis and the return to G1 in the two daughter cells. (B) The endocycle involves oscillations between a gap phase and S phase and can produce either polyploid or polytene cells, distinguished by whether the replicated chromatids remain in physical association. (C) Endomitosis is distinguished by entry into mitosis but a failure to complete all aspects of mitosis. This can involve a failure of nuclear envelope breakdown but assembly of a spindle within the nucleus and segregation of sister chromatids, nuclear envelope breakdown and anaphase segregation, or completion of all of the events of mitosis, including nuclear division, but without cytokinesis.