Biology
Cell Division: Mitosis and Meiosis
| Feature | Mitosis | Meiosis |
|---|---|---|
| Cell | somatic | sex (germ) |
| Division | 1 | 2 |
| Result | 2 (2n) | 4 (n) |
| Crossing over | no | yes |
Mitosis
Division of somatic cells. As a result, 2 diploid cells identical to the parent cell are formed.
Phases:
- Prophase: chromosomes condense (spiralize).
- Metaphase: chromosomes line up at the equator.
- Anaphase: chromatids move to the poles.
- Telophase: nuclei form.
Interphase includes the G₁, S (DNA doubles) and G₂ periods.
Meiosis
Formation of gametes. Two successive divisions produce 4 haploid cells.
- Meiosis I: reductional (homologous chromosomes separate).
- Meiosis II: equational (chromatids separate).
Key facts
- In humans, mitosis produces 46 chromosomes from 46, and meiosis produces 23 from 46.
- Conjugation and crossing over occur in prophase of meiosis I. They ensure genetic diversity.
- Significance of mitosis: growth, regeneration, asexual reproduction. Significance of meiosis: formation of gametes and spores.
- In anaphase of mitosis, the number of chromosomes temporarily doubles (4n4c), because the chromatids become independent chromosomes.
- DNA reduplication occurs in the S period (replication).