Cell cycle
eukaryotic cell from one cell division to the next. It consists of interphase, mitosis, and usually cell division.
Phases
Schematic of the cell cycle. I=Interphase, M=Mitosis.
The duration of mitosis in relation to the other phases has
been exaggerated in this diagram.
The phases of the cell cycle are:
- The G1 phase is the first growth phase.
- The G0 phase is a period in the cell cycle where cells exist in a quiescent state.
- S phase, during which the DNA is replicated, where S stands for the Synthesis of DNA.
- G2 phase is the second growth phase, also the preparation phase for the
- M phase or mitosis and cytokinesis, the actual division of the cell into two daughter cells
Checkpoints can block progression through the phases of the cell cycle if certain conditions are not met. For instance, there is a checkpoint which monitors DNA replication and keeps cells from proceeding to mitosis before DNA replication is completed. Similarly, the spindle checkpoint blocks the transition from metaphase to anaphase within mitosis if not all chromosomes are attached to the mitotic spindle.
Some cells, such as neurons, never divide once they become locked in a G0 phase.
Regulation of the cell cycle
The cell cycle is regulated by cyclins and cyclin-dependent kinases.
Leland H. Hartwell, R. Timothy Hunt, and Paul M. Nurse won the 2001 Nobel Prize in Physiology or Medicine for their discovery of cyclin and cyclin-dependent kinase, central molecules in the regulation of the cell cycle.
