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G 2 phase, Gap 2 phase, or Growth 2 phase, is the third subphase of interphase in the cell cycle directly preceding mitosis. It follows the successful completion of S phase, during which the cell’s DNA is replicated. G 2 phase ends with the onset of prophase, the first phase of mitosis in which the cell’s chromatin condenses into chromosomes.
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
The main rad3 effector is the kinase Chk1, which is required for the G2-M arrest in response to DNA-damaging agents. [9] Chk1 is an effector protein kinase that maintains mitotic cyclin in an inactive state and is phosphorylated by rad3 between S phase and mitosis, implicating its specific role in G2 arrest. [10]
The G2 to M transition is dramatic; there is an all-or-nothing effect, and the transition is irreversible. This is advantageous to the cell because entering mitosis is a critical step in the life cycle of a cell. If it does not fully commit, the cell would run into many issues with partially dividing, ultimately likely leading to the cell's death.
Interphase is the active portion of the cell cycle that includes the G1, S, and G2 phases, where the cell grows, replicates its DNA, and prepares for mitosis, respectively. Interphase was formerly called the "resting phase," but the cell in interphase is not simply dormant.
In S phase, the chromosomes are replicated in order for the genetic content to be maintained. [18] During G 2, the cell undergoes the final stages of growth before it enters the M phase, where spindles are synthesized. The M phase can be either mitosis or meiosis depending on the type of cell.
These neurons are able to enter the S phase and replicate their DNA, however they become blocked in the G2 state. In affected and unaffected tetraploid neurons, during development and during the progression of the disease, passing the G2/M checkpoint leads to cell death. This hints that the G2/M checkpoint aids in the survival of tetraploid ...
G2 is commenced by E2F-mediated transcription of cyclin A, which forms the cyclin A-Cdk2 complex. In order to proceed into mitosis, the cyclin B-Cdk1 complex (first discovered as MPF or M-phase promoting factor; Cdk1 is also known as Cdc2 in fission yeast and Cdc28 in budding yeast) is activated by Cdc25, a protein phosphatase. [1]