meiozis

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, often called the reductional division, is where homologous chromosomes separate. It begins with prophase I, during which chromosomes condense and homologous chromosomes pair up in a process called synapsis, forming tetrads. Crossing over, the exchange of genetic material between non-sister chromatids, occurs during prophase I, contributing to genetic diversity. Metaphase I involves the alignment of homologous pairs at the metaphase plate. In anaphase I, homologous chromosomes are pulled apart to opposite poles of the cell. Telophase I results in two haploid cells, each containing one chromosome from each homologous pair, but each chromosome still consists of two sister chromatids.

Meiosis II, the equational division, is similar to mitosis. It begins with prophase II, where chromosomes condense again. In metaphase II, chromosomes align at the metaphase plate. Anaphase II sees the separation of sister chromatids, which are then pulled to opposite poles. Finally, telophase II and cytokinesis result in four genetically unique haploid daughter cells, each with a single set of chromosomes. These haploid cells develop into gametes (sperm and egg cells) or spores.