1. Introduction to Cell Division
- Cell division is the process by which a parent cell divides into two or more daughter cells.
- It is essential for growth, repair, reproduction, and maintenance of organisms.
- There are two main types of cell division: Mitosis and Meiosis.
2. Mitosis
- Mitosis is the process of nuclear division that produces two genetically identical daughter cells.
- It occurs in somatic cells and is responsible for growth and tissue repair.
- The number of chromosomes remains unchanged (diploid to diploid).
- The phases of mitosis include:
- Prophase: Chromatin condenses into visible chromosomes, and the nuclear envelope dissolves.
- Metaphase: Chromosomes align at the metaphase plate (cell equator).
- Anaphase: Sister chromatids are pulled apart to opposite poles.
- Telophase: Nuclear membranes reform, and chromosomes decondense.
- Cytokinesis follows mitosis, dividing the cytoplasm to form two distinct cells.
3. Meiosis
- Meiosis is a type of cell division that results in four genetically unique daughter cells.
- Occurs in germ cells to produce gametes (sperm and egg cells).
- It reduces the chromosome number from diploid (2n) to haploid (n).
- Consists of two successive divisions: Meiosis I and Meiosis II.
- Phases of Meiosis I:
- Prophase I: Homologous chromosomes undergo crossing over (genetic recombination).
- Metaphase I: Homologous chromosomes align at the metaphase plate.
- Anaphase I: Homologous chromosomes separate (sister chromatids remain together).
- Telophase I: Two haploid cells are formed.
- Phases of Meiosis II: Similar to mitosis but results in four haploid cells.
4. Differences Between Mitosis and Meiosis
| Feature | Mitosis | Meiosis |
|---|---|---|
| Type of Cells | Somatic cells | Germ cells |
| Number of Divisions | One | Two |
| Number of Daughter Cells | Two | Four |
| Chromosome Number | Same as parent (2n) | Half of parent (n) |
| Genetic Variation | No | Yes (due to crossing over) |
| Function | Growth and repair | Sexual reproduction |
5. Significance of Cell Division
- Mitosis ensures growth, repair, and asexual reproduction in multicellular organisms.
- Meiosis maintains genetic diversity and the stability of chromosome numbers across generations.
- Cell division is crucial for the replacement of damaged or dead cells.
- It allows organisms to adapt and evolve through genetic variations.
6. Conclusion
- Mitosis produces two genetically identical cells for growth and repair.
- Meiosis creates genetically unique gametes for sexual reproduction.
- Both processes are vital for the continuity of life and genetic stability.