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Cell Cycle, Mitosis, and Meiosis

The Cell Cycle

Definition
The cell cycle is the cyclic series of cell divisions (mitoses) and growth phases (interphases) that occur in dividing (proliferating) tissues.
Fig.1
Schematic of cell division sequence
Mariana Ruiz Villarreal (this work is public domain)

In the tissues of multicellular organisms, spent and dead cells are replaced through cell division. In growing organisms, cell division is responsible for growth. The cell cycle regulates and coordinates cell reproduction. In this process, the DNA must first be duplicated (replicated) and the chromosomes that result from this must be correctly divided between the two daughter cells. In addition, most cells must double their mass and organelles beforehand. The chronological progression of these manifold processes is coordinated by the cell cycle.

The period between cell divisions, which are called the mitotic phases (M phase or mitosis), is referred to as the interphase. During this phase, the cell grows to the necessary size and many molecular processes, most prominently the replication of DNA, occur. The interphase is subdivided into three distinct phases known as G1 (abbreviation for Gap 1), S (synthesis), and G2.

Within the cell cycle, the interactions of various proteins are interpreted as stop or go/start signals for specific phases (checkpoints) of the cell cycle. The two most important checkpoints are immediately preceding entry into the S phase (G1 checkpoint) and just before beginning mitosis (G2 checkpoint).

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Fig.2
The cell cycle

Schematic of the cell cycle: The cell cycle consists of a chronological sequence of different phases: G1 (gap), possibly G0, S(ynthesis), G2 , and M(itosis). Three checkpoints (G1, G2 , and M) regulate the continuation or interruption of the cell cycle.

For their discovery of the key regulators of the cell cycle, American Leland Hartwell and Britons Paul Nurse and Tim Hunt received the 2001 Nobel Prize in Physiology or Medicine.

G1 phase

G0 phase

S phase

G2 phase

M phase

Additional information

Der Zellzyklus (Navigation: Biologie/Cytologie/Zellzyklus, German)

The Cell Cycle

Literature

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