Cell cycle

The cell cycle consists of an interphase during which growth of the cell (G1) occurs, the cell increases in volume to maximum size and there is synthesis of cytoplasmic constituents and RNA. Synthesis of DNA occurs next, during the S phase, as chromo- somes are duplicated in preparation for nuclear division. During the final part of the cell cycle a second gap or growth phase occurs (G2), when specific cell division-related proteins are synthesized. Nuclear division (M) then follows to complete the cell cycle.

Figure:  The eukaryotic cell cycle. The S phase is typically 6–8 hours  long,  G2  is a phase in which the  cell prepares for mitosis  and  lasts for 2–6 hours,  mitosis  itself (M) is short  and  takes only about 1 hour.  The length of G1 is very variable and depends on the cell type.  Cells can enter G0, a quiescent phase, instead of continuing with the cell cycle.