By Kevin Beck, Updated Aug 30, 2022

When a eukaryotic cell completes its life cycle, it divides into two daughter cells, each inheriting a full copy of the parent’s DNA. This final division, called cytokinesis, follows mitosis—the multi‑step process that splits the nucleus into two.

The Eukaryotic Cell Cycle

Eukaryotes (plants, animals, fungi) possess nuclei and organelles, making their division more complex than that of prokaryotes, which reproduce by binary fission. A eukaryotic cell enters the G1 (first gap) phase of interphase, where it grows. DNA replication occurs in the S (synthesis) phase, followed by a second gap (G2) where the cell checks its replication. Finally, the M (mitosis) phase culminates in both nuclear and cytoplasmic division. Interphase occupies the majority of the cycle, while the M phase is brief but critical.

The Stages of Mitosis

Mitosis is traditionally divided into five stages, offering a complete view of nuclear division:

• Prophase: Chromosomes condense and become visible. Centrioles duplicate and migrate to opposite poles, initiating the mitotic spindle.
• Prometaphase: The nuclear envelope dissolves, and spindle microtubules attach to kinetochores, guiding chromosomes toward the equator.
• Metaphase: Chromosomes align precisely along the metaphase plate, ensuring equal distribution of sister chromatids.
• Anaphase: Sister chromatids separate, pulled to opposite poles by shortening spindle fibers. The cleavage furrow appears, signaling the onset of cytokinesis.
• Telophase: Chromatids decondense, new nuclear envelopes form around each set, and the cell prepares for cytoplasmic division.

Cytokinesis Overview

Although often presented as a discrete event after mitosis, cytokinesis actually overlaps temporally with late mitotic stages. The cleavage furrow that initiates division appears during anaphase, ensuring that chromatids are already segregated before the plasma membrane pinches inward. This overlap safeguards genomic integrity by preventing asymmetrical chromosome distribution.

The Contractile Ring

Central to animal cell cytokinesis is the contractile ring, a dynamic scaffold of actin filaments and myosin motors situated just beneath the plasma membrane. As the ring contracts, the membrane indents to form the cleavage furrow. New membrane material is supplied from vesicles, sealing the emerging daughter cells. Plant cells, with rigid cell walls, rely on a different mechanism that does not involve a visible furrow.

Asymmetric Division

Cells can divide asymmetrically, distributing cytoplasmic contents unevenly while maintaining equal chromosomal segregation. This strategy enables daughter cells to acquire distinct fates or functions—an essential process in development, stem cell differentiation, and specialized tissue formation.