The cell cycle is the process by which cells grow, replicate their genetic material, and divide. In eukaryotes, cell division is known as mitosis. The entire cell cycle is divided into four phases: G1, S, G2, and M. The G1, S, and G2 phases are collectively known as interphase. During interphase, a cell grows, replicates its genetic material, and continues growing. The cell then moves to the M phase. The M phase is divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Telophase includes cytokinesis, the pinching off of the cytoplasm to make two cells. Following the M phase, the cells may reenter the cell cycle or they may exit it and stop dividing, depending on the type of cell. Prokaryotes, which are unicellular organisms, follow a pathway called binary fission, and their cell division is a method of asexual reproduction.
At A Glance
- The cell cycle is the continuum of cell growth and division in the life of a cell. Cell division in eukaryotes is called mitosis.
- The cell cycle consists of interphase and mitosis.
- During interphase, comprised of the G1, S, and G2 phases of the cell cycle, the cell grows, replicates its DNA, then grows some more.
Mitosis divides the DNA in the steps prophase, prometaphase, metaphase, anaphase, and telophase. The end of mitosis is followed by cytokinesis, forming two cells identical to the parent cell.
Prophase is the first phase of mitosis, where the nucleus dissolves and the DNA condenses into chromosomes.
- During prometaphase, the nuclear membrane starts to dissolve and the chromosomes start to move towards the spindle fibers.
Metaphase is the third phase of mitosis, where the chromosomes align themselves along the equator of the cell.
Anaphase is the fourth phase of mitosis, where the sister chromatids separate and start to move towards opposite sides of the cell.
- During telophase the nuclear membrane reforms and prepares the cell to divide in half during cytokinesis.
- The cell cycle is tightly regulated by genetic signals and external signals.
- The cell-cycle-control system regulates cell growth and division by a series of checkpoints that are controlled by the interaction of cyclin-dependent kinases and cyclins.
Cancer is uncontrolled cell growth and division.
- Prokaryotes reproduce asexually through binary fission.