1. Mitosis:
* Purpose: Growth and repair of tissues. Produces two identical daughter cells from a single parent cell.
* Steps:
* Interphase: The cell grows, copies its DNA, and prepares for division.
* Prophase: The chromosomes condense and become visible, the nuclear envelope breaks down, and spindle fibers form.
* Metaphase: The chromosomes line up at the center of the cell.
* Anaphase: The sister chromatids (identical copies of each chromosome) are pulled apart to opposite poles of the cell.
* Telophase: The chromosomes uncoil, the nuclear envelope reforms, and the cytoplasm divides (cytokinesis) to form two daughter cells.
2. Meiosis:
* Purpose: Sexual reproduction, producing gametes (sperm and egg cells). Produces four daughter cells, each with half the number of chromosomes as the parent cell.
* Steps:
* Meiosis I: Similar to mitosis, but with an additional step where homologous chromosomes (one from each parent) pair up and exchange genetic material (crossing over).
* Meiosis II: Similar to mitosis, but with half the number of chromosomes.
Key processes involved in cell division:
* DNA replication: The cell's DNA is copied exactly, ensuring each daughter cell receives a complete set of genetic instructions.
* Chromosome segregation: The duplicated chromosomes are separated and distributed equally to the daughter cells.
* Cytokinesis: The cytoplasm divides, forming two separate cells.
Control of cell division:
* Cell cycle checkpoints: These ensure that the cell division process is accurate and only occurs when appropriate.
* Growth factors: These proteins stimulate cell growth and division.
* Tumor suppressor genes: These genes prevent uncontrolled cell division and help protect against cancer.
Importance of cell division:
* Growth: Enables multicellular organisms to grow and develop.
* Repair: Replaces damaged or worn-out cells.
* Reproduction: Creates new organisms through sexual or asexual reproduction.
In summary, cell division is a complex and tightly regulated process that ensures the continuity of life. Mitosis creates identical copies for growth and repair, while meiosis generates genetic diversity for sexual reproduction.
