5.1.3—Mitotic cell cycle

The cell cycle is the regulated sequence from one cell division to the next. Interphase prepares the cell and copies its DNA, mitosis divides the nucleus, and cytokinesis divides the cytoplasm to form separate daughter cells.

1. G1 — growth and normal activity: The cell grows and carries out its usual synthesis and functions, building the material needed for a later division.
2. S phase — DNA replication: The cell copies its DNA. Each chromosome is thereby prepared as a replicated chromosome with matching sister chromatids; the cell has not yet divided.
3. G2 — further preparation: The cell continues to grow and prepares for nuclear division, including checking that the copied genetic material and division machinery are ready.
4. Interphase result: G1, S and G2 together prepare one cell with duplicated genetic material for the accurate separation of matching copies.
5. Mitosis — nuclear division: The replicated chromosome copies are separated into two genetically matching nuclei with the same chromosome number as the parent nucleus.
6. Cytokinesis — cytoplasmic division: The cytoplasm and cell boundary partition around the nuclei, producing two separate daughter cells. Animal cells constrict; plant cells build a new partition.

DNA replication must occur before chromosome copies are distributed: without two matching copies, each daughter nucleus could not receive a complete corresponding set. Mitosis handles nuclear distribution; cytokinesis completes the physical separation of the daughter cells.

Interphase is active preparation, not a single resting stage, and S phase is DNA replication rather than mitosis. Mitosis divides the nucleus; cytokinesis divides the cytoplasm. The broader biological importance of the resulting matching cells belongs to card 4561, while telomere buffering belongs to card 4563.