🔀 Cell division
Red = maternal · Blue = paternal · 2 of 23 human pairs shown
Interphase (G1 → S → G2)
The cell grows (G1), copies every chromosome in S phase, then checks the copies and grows more (G2). ~90% of the cycle is spent here.
- Chromosomes
- 2n · DNA doubles from 2C to 4C in S phase
- Checkpoint
- G1/S ‘restriction point’ — is the cell big enough, is DNA undamaged? (controlled by p53, Rb, cyclin D–CDK4/6)
| Purpose | Growth, repair, asexual reproduction | Sexual reproduction (gametes) |
|---|---|---|
| Divisions | 1 | 2 |
| Daughter cells | 2, diploid (2n) | 4, haploid (n) |
| Genetically | Identical | All different |
| Crossing over | No | Yes, prophase I |