The cell cycle is the lifecycle of a cell. During this cycle, cell grows and divides.
Normal cells, however, move through the cell cycle in a regulated way.
They use information about their own internal state and cues from the environment around them to decide whether to proceed with celldivision.
This regulation makes sure that cells don't divide under unfavorable conditions (for instance, when their DNA is damaged, or when there isn't room for more cells in a tissue or organ).
Interphase
In interphase, the cell grows and takes in nutrients in preparation for division. Interphase takes up about 90 percent of the cell cycle.
It consists of three parts: Gap1, Synthesis, and Gap2.
A cell moves through a series of phases in an orderly manner. During interphase,
G1
involves cell growth and protein synthesis, the
Gap 1 (G1) is also known as a growth phase. The cell gets larger and increases its stock of proteins, along with organelles such as the energy-producing mitochondria
During interphase,
2. Sphase
involves DNAreplication and the replication of the centrosome, and
Synthesis (S) is the phase in which DNA replicates. During synthesis, the chromosomes replicate so that each chromosome is made up of twosisterchromatids. At the end of this phase, there is double the amount of DNA in the cell.
During interphase,
3. G2
involves further growth and protein synthesis.
Gap 2 (G2) is another growth phase. The cell becomes even larger in order to prepare for mitotic division.
Quiescence (Go)
, also known as senescence or resting, is a phase in which the cell is notactivelydividing.
It is also known as Gap 0, or Go.
This stage is considered the start of the cell cycle, although it is one that cells can reach and then stop dividing indefinitely, which ends the cell cycle.
Spinalchord, Liver, stomach, kidney cells, and neuron are all examples of cells that can reach this stage and remain in it for long periods of time. cell's DNA is damaged.
MitoticPhase
The mitotic phase follows interphase.
Mitosis - is nuclear division during which duplicatedchromosomes are segregated and distributed into daughter nuclei.
Usually the cell will divide after mitosis in a process called cytokinesis in which the cytoplasm is divided and twodaughtercells are formed.
Mitotic Phase
Mitosis, or M phase, is when the cell begins to organize its duplicatedDNA for separation into two daughter cells.
The chromosomes separate so that one of each chromosome goes into each daughter cell.
This results in the daughter cells having identical chromosomes to the
Mitosis itself is divided into:
prophase,
metaphase
anaphase, and
telophase, which mark various points in the DNA separation process. Mitosis is then followed by a process called cytokinesis, during which the cell separates its nuclei and other organelles in preparation for division and then physically divides into two cells
The Cell Cycle and the Checkpoint
The cell cycle is controlled at three checkpoints. The integrity of the DNA is assessed at the G1 checkpoint. Proper chromosome duplication is assessed at the G2 checkpoint. Attachment of each kinetochore to a spindle fiber is assessed at the M checkpoint
Cell cycle checkpoints
A checkpoint is a stage in the eukaryotic cell cycle at which the cell examines internal and external cues and "decides" whether or not to move forward with division. There are a number of checkpoints, but the three most important ones are
Cell cycle checkpoints
Cell Growth Checkpoint
DNA Synthesis Checkpoint
Mitosis Checkpoint
Cell cycle checkpoints
Cell Growth Checkpoint
Occurs toward the end of growth phase 1 (G1) .
Checks whether the cell is big enough and has made the proper proteins for synthesis phase
If not, the cell goes through a resting period (GO) until it is ready to divide