Overview
This lecture explains mitosis, the process by which body cells divide for growth and repair, including the key stages and its biological importance.
Functions and Importance of Mitosis
- Mitosis enables organisms to grow by producing more cells.
- It repairs damage, replacing lost or worn out cells (e.g., healing cuts).
- Mitosis creates identical body cells, crucial for tissue maintenance.
- Uncontrolled mitosis leads to cancer, defined as uncontrolled cell growth.
What Mitosis Is and Is Not
- Mitosis is used by body (somatic) cells, not for producing sperm or egg cells.
- Meiosis, not mitosis, produces sperm and egg cells.
- Mitosis results in genetically identical cells with the same number of chromosomes as the original.
The Cell Cycle and DNA Organization
- Most cells spend their time in interphase, not mitosis.
- Interphase involves cell growth, DNA replication, and preparing for division.
- The nucleus holds DNA, which must be identical in new cells.
- DNA condenses into chromosomes for easier distribution during mitosis.
- Human body cells have 46 chromosomes per nucleus.
- Chromosome duplication occurs in interphase; chromatids double but chromosome count by centromeres stays 46.
Stages of Mitosis (PMAT)
- Prophase: Chromosomes condense and become visible; nucleus is still present.
- Metaphase: Chromosomes align in the cell's middle; nucleus disappears.
- Anaphase: Chromosomes (sister chromatids) are pulled apart to opposite poles of the cell by spindle fibers.
- Telophase: Chromosomes reach poles; new nuclei form around chromosomes, preparing for two identical cells.
Cytokinesis
- Cytokinesis is the division of the cytoplasm, finalizing the creation of two separate, identical cells after mitosis.
Key Terms & Definitions
- Mitosis — cell division process creating identical body cells.
- Meiosis — cell division process producing sperm and egg cells with half the original chromosomes.
- Interphase — phase where the cell grows and duplicates DNA before division.
- Nucleus — organelle holding genetic material (DNA).
- Chromosome — condensed structure of DNA and protein for organizing genetic material.
- Chromatid — one-half of a duplicated chromosome.
- Centromere — region joining two sister chromatids.
- Spindle fibers — structures that move chromosomes during mitosis.
- Cytokinesis — division of cytoplasm, completing cell division.
Action Items / Next Steps
- Review the stages of mitosis using the PMAT acronym.
- Watch clips on the cell cycle and chromosome number for deeper understanding.