Cue Column | Notes Column
| Cue | Notes |
|---|---|
| What is the cell cycle? | Ordered sequence of events: cell duplicates contents and divides. Two major phases: Interphase (~95%) and M phase (~5%). |
| What happens in G1? | Active RNA + protein synthesis; cell growth; DNA content = 2C; chromosome count = 2n. Variable duration. |
| What happens in S phase? | DNA replication. DNA doubles: 2C → 4C. Chromosome number stays 2n (sister chromatids joined at centromere). Duration: 6–8 hours. |
| What happens in G2? | Tubulin synthesis for spindle; final preparations. DNA = 4C, chromosomes = 2n. Duration: 3–4 hours. |
| What is G0? | Quiescent/resting state. Cells exited the cycle. Examples: neurons, mature RBCs. Some G0 cells can re-enter (liver cells); others cannot (neurons, RBCs). |
| What is M phase? | Nuclear division (karyokinesis: prophase → metaphase → anaphase → telophase) + cytoplasmic division (cytokinesis). Duration: ~1 hour. |
Summary Box
The cell cycle is G1 → S → G2 → M phase, with interphase (G1+S+G2) taking ~95% of the time. G0 is a side exit from G1 for non-dividing cells. S phase doubles DNA (not chromosomes). G2 prepares the spindle.