Cell Division Why do our hair and nails grow longer? Or why can injured skin heal? These two events are proof that our body cells can divide. How do cells divide? Cell division can occur directly or indirectly. Direct cell division is called amitosis. Amitosis occurs in bacteria to form new bacteria. The chromosomes in bacteria will duplicate and divide in two, then the cell membrane divides into two identical daughter cells. Indirect cell division can be done by mitosis or meiosis. Both methods must go through several phases or stages. The purpose of mitosis is to multiply cells or repair damaged cells. Mitosis will produce two daughter cells whose number of chromosomes and characteristics are identical to the parent cell. If the chromosomes of the parent cell are diploid, then the daughter cells are also diploid. Mitosis is part of the cell cycle. Mitosis is preceded by interphase which dominates the cell cycle. Interphase begins in the G1 phase, where the cell size increases. Followed by the S phase, where DNA synthesis and replication occurs. And finally the G2 phase, where the cell organelles have formed and the cell is ready to divide. After interphase, mitosis begins. First, in the prophase stage, the chromatin threads in the cell nucleus condense into chromosomes, then the chromosomes duplicate, and the nuclear membrane disappears. Then the metaphase stage, the chromosomes line up in the equatorial plane. Next, in the anaphase stage, each chromatid moves towards the opposite pole. Then in the telophase stage, the chromosomes at each pole return to chromatin and the nuclear membrane begins to reform. The final stage is cytokinesis, where the cytoplasm divides. So, for every cell that undergoes mitosis, two daughter cells will be produced. The purpose of meiosis is to form gamete cells. Meiosis occurs in two stages, namely meiosis I and meiosis II. Meiosis will reduce the number of chromosomes in the parent cell to half. If the chromosomes of the parent cell are diploid, then the daughter cells will be haploid. The characteristics of the daughter cells resulting from meiosis are also not identical to the parent because genetic recombination occurs at one of the stages. Meiosis begins with the interphase stage, where DNA replicates. Then enter prophase I, the longest phase in meiosis. Prophase I consists of 5 stages. First leptotene, chromatin threads condense into chromosomes. In the second zygote, homologous chromosomes pair and form synapses. In pachytene, homologous chromosomes duplicate into tetrads. In diplotene, homologous chromosome pairs form chiasmata that allow genetic recombination to occur. And fifth diakinesis, the nuclear membrane begins to disappear. Prophase I is then continued with metaphase I, where the tetrad chromosomes line up in the equatorial plane to form 2 rows of chromosomes. Then in anaphase I, the homologous chromosome pairs separate as they move towards opposite poles. In telophase and cytokinesis I, homologous chromosomes are at both poles and the cytoplasm divides into 2 daughter cells. At the end of meiosis I, the chromosomes of the diploid parent cell have been reduced to two haploid daughter cells. After meiosis I is complete, there are types of cells that immediately enter meiosis II or first experience the interkinesis phase. The phases in meiosis II are almost the same. Starting from prophase II, the chromosomes line up in a row, then the chromatids separate, and finally the cytoplasm divides. So, for every cell that undergoes meiosis, four daughter cells will be produced. Mitosis and meiosis division can occur in gametogenesis or the process of gamete cell formation. Gametogenesis in animals and humans consists of spermatogenesis to produce sperm cells, and oogenesis to produce egg cells or ovum. In spermatogenesis, stem cells or spermatogonia multiply their cells by mitosis. The spermatogonia then enlarge and duplicate their chromosomes to form primary spermatocytes. Primary spermatocytes undergo meiosis I division to become secondary spermatocytes. Then meiosis II continues to produce 4 spermatids. Spermatids undergo maturation to form 4 spermatozoa cells. Oogenesis has stem cells called oogonium. Oogonium reproduces its cells by mitosis. The oogonium duplicates its chromosomes to become a primary oocyte. The primary oocyte then undergoes meiosis I to become a secondary oocyte and a polar body. Both then undergo meiosis II. The secondary oocyte produces the ootid and polar body. While the polar body produces two other polar bodies. At the end of oogenesis, 1 mature ovum cell and 3 degenerated polar bodies are formed. How does gametogenesis occur in plants? Gametogenesis in angiosperms consists of microsporogenesis and megasporogenesis. Microsporogenesis to produce male gametes occurs in the pollen sacs, while megasporogenesis to produce female gametes occurs in the ovary. In microsporogenesis, the diploid microsporocyte mother cell undergoes meiosis to produce haploid microspores or pollen. After pollination, pollen will undergo karyokinesis or nuclear division without being followed by cytoplasmic division. Karyokinesis in pollen produces a tube nucleus and a generative nucleus. The generative nucleus will undergo karyokinesis again to become two sperm nuclei. In megasporogenesis, the megasporocyte mother cell undergoes meiosis to produce 1 functional megaspore and 3 degenerated megaspores. One functional megaspore will undergo karyokinesis 3 times producing 8 haploid nuclei. These 8 nuclei consist of 3 antipodes, 2 nuclei that merge to form the secondary embryo sac nucleus, 2 synergids, and 1 ovum. Wow, our discussion today is complete. To summarize, cell division in bacteria is carried out for reproduction, while in humans, animals and plants it is useful for growth and development, repairing damage and forming gamete cells for reproduction. Abnormal cell division can cause abnormalities. For example, Down syndrome is an abnormality caused by chromosomes that fail to separate, so that the chromosomes only move to one pole. In this case, which phase is running abnormally? Please write your answer in the comments column. If you want to practice more questions on the topic of 'Cell division', let's visit the kejarcita.id website or download the kejarcita application on the Play Store. Like and share this video with other cool friends too. pursuit of dreams. Pursue knowledge, achieve dreams.