Cell Cycle
The cell cycle is the ordered sequence of events by which a cell grows, replicates its DNA, and divides into two daughter cells. It consists of interphase (G1, S, and G2 phases) and the mitotic phase (mitosis and cytokinesis). Precise regulation of the cell cycle through checkpoints is essential for normal development; dysregulation leads to cancer and other diseases.
Phases of the Cell Cycle and Key Events
| Phase | Stage | Key Event | Approximate Duration (human cell) |
|---|---|---|---|
| Interphase | G1 (Gap 1) | Cell growth, protein synthesis | ~11 hours |
| Interphase | S (Synthesis) | DNA replication | ~8 hours |
| Interphase | G2 (Gap 2) | Growth, preparation for division | ~4 hours |
| M Phase | Mitosis | Nuclear division into two nuclei | ~1 hour |
| M Phase | Cytokinesis | Cytoplasm division, two daughter cells | ~30 minutes |
| Arrest | G0 | Quiescent or senescent state | Variable |
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Related Terms
Apoptosis
Apoptosis is a form of programmed, genetically regulated cell death that occurs in multicellular organisms as a normal and controlled part of development and homeostasis. It is characterised by cell shrinkage, chromatin condensation, membrane blebbing, and fragmentation into apoptotic bodies that are cleared by phagocytes without triggering inflammation. Dysregulation of apoptosis is implicated in cancer (insufficient apoptosis) and neurodegenerative diseases (excessive apoptosis).
Stem Cell
A stem cell is an undifferentiated cell capable of self-renewal and differentiation into specialised cell types. Stem cells are found in embryos (embryonic stem cells) and adult tissues (adult stem cells), serving as a repair and replenishment system throughout life. Their unique plasticity makes them central to regenerative medicine, disease modelling, and therapeutic research.
DNA
Deoxyribonucleic acid (DNA) is the double-stranded helical polymer that stores the genetic information of virtually all living organisms. It is composed of nucleotide monomers, each containing deoxyribose sugar, a phosphate group, and one of four nitrogenous bases: adenine (A), thymine (T), guanine (G), or cytosine (C), paired by complementary hydrogen bonds (A–T and G–C). The sequence of bases encodes instructions for building proteins and regulating cellular functions, passed faithfully to daughter cells through semiconservative replication.
From Latin "cella" (small room) + Greek "kyklos" (circle, wheel). The term was formalised in the 1950s following the discovery of the S phase by Alma Howard and Stephen Pelc using radioactive labelling techniques.