sejtciklus

Sejtciklus, or the cell cycle, is the series of orderly events by which a eukaryotic cell grows, duplicates its DNA, and divides. The cycle ensures genetic material is faithfully replicated and partitioned into two daughter cells. In most eukaryotic cells, the cycle is divided into interphase and the M phase. Interphase comprises G1 (growth and monitoring of the environment), S (DNA synthesis and replication), and G2 (further growth and preparation for mitosis). Many cells can enter a quiescent state, G0, in which division is paused. During the M phase, mitosis occurs followed by cytokinesis, giving two genetically identical daughter cells. Mitosis includes prophase, prometaphase, metaphase, anaphase, and telophase; cytokinesis completes cell division by physical separation.

The cycle is tightly regulated by cyclins and cyclin-dependent kinases (CDKs), whose activity is modulated by checkpoints that monitor DNA integrity, replication completion, and proper chromosome attachment to the spindle. External signals such as nutrients, growth factors, and cell density influence cycle progression. Meiosis is a specialized division in germ cells that reduces chromosome number and is separate from the standard somatic cell cycle, consisting of two consecutive divisions after a single DNA replication.

Dysregulation of sejtciklus control is a hallmark of many cancers and is a major target for therapies that inhibit CDKs or disrupt mitotic progression.