1. Introduction
- Cell division is the process by which a parent cell divides into two or more daughter cells.
- It plays a crucial role in growth, development, reproduction, and tissue repair.
- The two main types of cell division are Mitosis and Meiosis.
2. The Cell Cycle
- The cell cycle is the series of events that take place in a cell leading to its division.
- It consists of two main phases: Interphase and Mitotic (M) phase.
- Interphase is the longest phase, where the cell grows and prepares for division.
- Interphase consists of three sub-phases: G1 phase (growth phase), S phase (DNA replication), and G2 phase (preparation for mitosis).
- The M phase includes mitosis (or meiosis) and cytokinesis.
3. Mitosis
- Mitosis is a type of cell division that results in two genetically identical daughter cells.
- It occurs in somatic cells for growth and tissue repair.
- Mitosis consists of four stages: Prophase, Metaphase, Anaphase, and Telophase.
- Prophase: Chromosomes condense, spindle fibers form, and the nuclear membrane breaks down.
- Metaphase: Chromosomes align at the cell’s equator, attached to spindle fibers.
- Anaphase: Sister chromatids separate and move to opposite poles.
- Telophase: Nuclear membranes reform around two sets of chromosomes.
- Cytokinesis follows mitosis, dividing the cytoplasm to form two daughter cells.
- Mitosis ensures the genetic stability of cells.
4. Meiosis
- Meiosis is a type of cell division that results in four genetically unique daughter cells.
- It occurs in germ cells to produce gametes (sperm and egg cells).
- Meiosis consists of two divisions: Meiosis I and Meiosis II.
- Meiosis I reduces the chromosome number by half (reductional division).
- Meiosis II is similar to mitosis (equational division).
- Meiosis leads to genetic variation due to crossing over and independent assortment.
5. Differences Between Mitosis and Meiosis
| Feature | Mitosis | Meiosis |
|---|---|---|
| Type of Cells | Somatic (body) cells | Germ cells (sperm & egg) |
| Number of Divisions | One | Two |
| Number of Daughter Cells | Two | Four |
| Genetic Identity | Identical to parent cell | Genetically unique |
| Chromosome Number | Diploid (2n) | Haploid (n) |
| Purpose | Growth and repair | Sexual reproduction |
6. Significance of Cell Division
- Growth: Mitosis helps in the increase of cell number in multicellular organisms.
- Repair and Healing: Mitosis replaces damaged or dead cells.
- Asexual Reproduction: Many organisms reproduce via mitotic division.
- Genetic Variation: Meiosis creates genetic diversity through recombination.
- Continuity of Life: Cell division ensures the survival of species through reproduction.