Answer:
Meiosis is a type of cell division that occurs in sexually reproducing organisms, resulting in the formation of haploid cells (gametes) from diploid cells. The process of meiosis consists of two main stages: Meiosis I and Meiosis II.
Meiosis I:
1. Prophase I: Chromosomes condense, and homologous chromosomes pair up in a process called synapsis. Crossing-over, where genetic material is exchanged between homologous chromosomes, occurs during this phase.
2. Metaphase I: Paired homologous chromosomes (tetrads) line up along the cell's equator.
3. Anaphase I: Homologous chromosomes separate and move to opposite poles of the cell. Unlike in mitosis, the sister chromatids remain attached.
4. Telophase I: Chromosomes reach the poles, and the cell undergoes cytokinesis, resulting in two daughter cells, each with half the number of chromosomes as the original cell. Each chromosome still consists of two sister chromatids.
Meiosis II:
Meiosis II is similar to mitosis but involves the division of haploid cells produced in Meiosis I.
1. Prophase II: A new spindle apparatus forms in each of the two haploid cells.
2. Metaphase II: Chromosomes line up along the equator of each cell.
3. Anaphase II: Sister chromatids are finally separated and pulled to opposite poles of the cells.
4. Telophase II: Chromatids reach the poles, and nuclear membranes reform around each set of chromosomes. Cytokinesis occurs, resulting in a total of four haploid daughter cells, each genetically distinct due to the process of crossing-over in Meiosis I.
These four haploid daughter cells are gametes (sperm or egg cells in animals, or pollen and ovules in plants), and they have half the chromosome number of the original diploid cell. The stages of meiosis ensure genetic diversity in sexually reproducing organisms.
