1. Prophase:
* Chromatin Condensation: The loose DNA in the nucleus condenses into visible chromosomes, each consisting of two identical sister chromatids attached at the centromere.
* Nuclear Envelope Breakdown: The membrane surrounding the nucleus disintegrates.
* Spindle Formation: Microtubules, protein fibers, assemble into a spindle-shaped structure that will help separate the chromosomes.
* Centriole Migration: In animal cells, centrioles (organelles involved in microtubule assembly) migrate to opposite poles of the cell.
2. Metaphase:
* Chromosome Alignment: Chromosomes line up along the equator (the middle) of the cell, attached to the spindle fibers at their centromeres.
* Spindle Fiber Attachment: Each sister chromatid is attached to a spindle fiber from opposite poles of the cell.
3. Anaphase:
* Sister Chromatid Separation: The centromeres of the chromosomes split, and the sister chromatids separate, moving towards opposite poles of the cell.
* Chromatid Movement: Spindle fibers shorten, pulling the chromatids apart.
4. Telophase:
* Nuclear Envelope Reformation: New nuclear envelopes form around the two sets of chromosomes at opposite poles of the cell.
* Chromatin Uncoiling: The chromosomes uncoil and become less visible as they return to their less condensed state.
* Cytokinesis: The cytoplasm divides, separating the two daughter cells. This process differs in animal and plant cells.
Cytokinesis: This is the process of dividing the cytoplasm and is not strictly a part of mitosis but occurs concurrently.
* Animal cells: A cleavage furrow forms, pinching the cell membrane inward until the two daughter cells are completely separated.
* Plant cells: A cell plate forms, eventually becoming the new cell wall that separates the two daughter cells.
Mitosis is essential for:
* Growth and Development: It allows organisms to grow by increasing the number of cells.
* Repair and Renewal: It replaces damaged or worn-out cells in the body.
* Asexual Reproduction: Some organisms reproduce asexually through mitosis.
Overall, mitosis is a crucial process that ensures the accurate duplication of genetic material and the creation of two identical daughter cells, playing a vital role in maintaining the integrity of an organism.
