meiózisos

Meiosis is a specialized type of cell division that reduces the chromosome number by half, creating four genetically distinct haploid cells. This process is essential for sexual reproduction in eukaryotic organisms. It occurs in two successive nuclear divisions, meiosis I and meiosis II, following a single round of DNA replication.

Meiosis I begins with prophase I, where homologous chromosomes pair up and exchange genetic material through crossing over. This recombination shuffles alleles and increases genetic diversity. Then, in metaphase I, these homologous pairs align at the metaphase plate. Anaphase I separates the homologous chromosomes, with each daughter cell receiving one chromosome from each pair. Telophase I and cytokinesis result in two haploid cells.

Meiosis II is similar to mitosis. In prophase II, chromosomes condense. In metaphase II, chromosomes align individually at the metaphase plate. Anaphase II separates the sister chromatids, which then move to opposite poles. Finally, telophase II and cytokinesis produce a total of four haploid daughter cells, each with half the chromosome number of the original diploid cell. These haploid cells are gametes (sperm and egg cells) or spores. The genetic variation introduced by crossing over and independent assortment of homologous chromosomes ensures that offspring are genetically unique.