Cellcyklen

Cellcyklen, also known as the cell division cycle, is a series of events that takes place in a cell leading to its division and duplication. This fundamental process ensures the growth and reproduction of all living organisms. The cell cycle is tightly regulated to ensure that new cells are identical to the parent cell and that cells divide only when necessary.

The cell cycle is typically divided into two main phases: interphase and the mitotic phase (M phase). Interphase is the longest phase, during which the cell grows, replicates its DNA, and prepares for division. It is further subdivided into G1 (first gap), S (synthesis), and G2 (second gap) phases. In G1, the cell grows and synthesizes proteins. In S phase, DNA replication occurs, resulting in two identical sets of chromosomes. G2 phase is another period of growth and preparation, where the cell checks for any errors in DNA replication.

The mitotic phase, or M phase, is the actual division of the cell. It involves mitosis, where the nucleus divides, and cytokinesis, where the cytoplasm divides, resulting in two daughter cells. Mitosis is further divided into prophase, metaphase, anaphase, and telophase. During prophase, chromosomes condense. In metaphase, chromosomes align at the center of the cell. Anaphase sees the sister chromatids separate and move to opposite poles. Finally, in telophase, new nuclear envelopes form around the separated chromosomes.

The cell cycle is controlled by a complex network of regulatory proteins, including cyclins and cyclin-dependent kinases (CDKs). These proteins act as checkpoints, ensuring that the cell cycle progresses only when conditions are favorable for division. Errors in cell cycle regulation can lead to uncontrolled cell proliferation, a hallmark of cancer.