Mitosis
* Purpose: To create two identical daughter cells with the same number of chromosomes as the parent cell. This is essential for growth, repair, and development.
* Process:
1. Interphase: The cell grows and copies its DNA (chromosomes). This is the longest phase of the cell cycle.
2. Prophase: The chromosomes condense and become visible. The nuclear envelope breaks down, and the spindle fibers begin to form.
3. Metaphase: The chromosomes line up at the center of the cell (metaphase plate).
4. Anaphase: The sister chromatids (identical copies of each chromosome) are pulled apart to opposite poles of the cell.
5. Telophase: The chromosomes arrive at the poles and begin to uncoil. The nuclear envelope reforms around each set of chromosomes, and the cytoplasm divides (cytokinesis).
Meiosis
* Purpose: To produce gametes (sex cells) with half the number of chromosomes as the parent cell. This ensures that when two gametes fuse during fertilization, the offspring will have the correct number of chromosomes.
* Process:
1. Meiosis I: This is essentially a reduction division, reducing the number of chromosomes from diploid (2n) to haploid (n).
* Prophase I: Chromosomes pair up and exchange genetic material (crossing over), creating genetic diversity.
* Metaphase I: Homologous chromosome pairs line up at the metaphase plate.
* Anaphase I: Homologous chromosome pairs are pulled apart, each going to opposite poles.
* Telophase I: The cytoplasm divides, resulting in two daughter cells, each with half the number of chromosomes.
2. Meiosis II: This is similar to mitosis, except that the starting cells are already haploid.
* Prophase II: Chromosomes condense.
* Metaphase II: Chromosomes line up at the metaphase plate.
* Anaphase II: Sister chromatids are pulled apart to opposite poles.
* Telophase II: The cytoplasm divides, resulting in four haploid daughter cells (gametes).
Key Differences:
* Number of divisions: Mitosis has one division, while meiosis has two.
* Number of daughter cells: Mitosis produces two daughter cells, while meiosis produces four.
* Chromosome number: Mitosis maintains the same number of chromosomes as the parent cell, while meiosis reduces the number of chromosomes by half.
* Genetic diversity: Mitosis produces genetically identical daughter cells, while meiosis produces genetically diverse daughter cells due to crossing over.
In summary, mitosis is essential for growth and repair, while meiosis is essential for sexual reproduction and genetic diversity.
