Summary
The ordered sequence of growth, DNA replication and division: G1, S, G2 and the mitotic phase.
In depth
Interphase comprises G1 (growth), S (DNA synthesis) and G2 (preparation); then M phase includes mitosis and cytokinesis. Cells that stop dividing enter G0, as neurons do. A typical human cell cycle lasts about 24 hours, with most of it spent in interphase.
After S phase each chromosome consists of two sister chromatids joined at a centromere. The cycle is regulated internally and by external signals such as growth factors.
Remember: DNA content doubles during S phase and returns to normal after cell division.
Cell cycle lengths vary widely: early frog embryos divide every 30 minutes with almost no gaps, while liver cells may divide only once a year or after injury. Control depends on the balance of growth signals and checks. Duplicating the centrosome, replicating DNA from thousands of origins and cohesion between sister chromatids by cohesin are all coordinated in time.
DNA replication is licensed once per cycle: origins are marked in G1 and can fire only in S phase, so no segment is copied twice.
Key idea: cells commit at the restriction point in late G1; before it they need growth factors, after it they proceed even if the signal is removed.
Frequently asked questions
What is Cell Cycle?
The ordered sequence of growth, DNA replication and division: G1, S, G2 and the mitotic phase.
Which area of biology covers Cell Cycle, and how advanced is it?
Cell Cycle is one of the 52 topics in Cell Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Cell Cycle Checkpoints, Mitosis, Nuclear Pore Complex.
What should I learn before Cell Cycle?
Work through the Beginner topics in Cell Biology first, such as Cell Theory, Prokaryotic Cell, Eukaryotic Cell, then return to Cell Cycle. Intermediate topics assume the Beginner vocabulary.
What topics are related to Cell Cycle?
The closest topics to Cell Cycle are Cell Cycle Checkpoints, Mitosis, Nuclear Pore Complex, Microtubule Dynamics. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Cell Cycle?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Cell Cycle. To practise the whole of Cell Biology, use the Cell Biology quiz.
How is Cell Cycle different from Cell Cycle Checkpoints?
Cell Cycle: The ordered sequence of growth, DNA replication and division: G1, S, G2 and the mitotic phase. Cell Cycle Checkpoints: Control points at G1/S, G2/M and metaphase that halt the cycle until DNA and spindle attachments are correct. Read both side by side and note what each one explains.
How should I study Cell Cycle step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Cell Cycle Checkpoints and explain the difference aloud. Finally, take the Cell Biology quiz and come back to this page for any question you miss.