The cell cycle consists of two major subdivisions. In the most visible and shortest portion, mitosis, a somatic cell divides into two daughter cells in which the chromosome number of the parental cell is maintained. The second portion of the cell cycle, interphase, separates successive mitoses and consists of three phases: G1, a period of cell growth; S, the phase in which DNA and diplosome replication occurs; and G2, a second period growth and preparation for mitosis. Typical eukaryotic cells complete the cell cycle in about 24 hours.
Mitosis is the process whereby cells divide to produce two identical daughter cells. Mitosis is the portion of the cell cycle during which chromosomal segregation (karyokinesis) and cell division (cytokinesis) occurs.
Interphase is the portion of the cell cycle that separates successive mitoses and consists of three phases: a subdivision of cell growth (G1); the portion where DNA and the diplosome are replicated (S); and a second period of cell growth in preparation for mitosis (G2).
- G1 phase >
During G1 phase, the cell increases in size and increases the number of organelles, e.g., mitochondria and ribosomes.
- S phase >
During S phase or synthesis phase, nuclear DNA is replicated. Duplication of the diplosome begins at the interface of the G1/S phases.
- G2 phase >
During G2 phase, the cell prepares for mitosis by further cell growth and increased protein synthesis.
G0 phase >
The G0 phase is not a part of the cell cycle. Rather, cells in the G0 phase have exited the cell cycle and, therefore, are no longer dividing. Under certain conditions, G0 cells can re-enter the cell cycle.