MODULE 12 (GAMETOGENESIS: SPERMATOGENESIS & OOGENESIS)

• Gamete formation is important for multicellular organism not only for reproduction but also to ensure the genetic variability.
• Two components of gametogenesis: spermatogenesis and oogenesis.
• Mitosis is a mechanism of cell division by which the genetic and chromosome composition of a cell is faithfully reproduced in each of the daughter cells.
• Meiosis is special type of cell division occurs in sexually reproducing cells.
• The process of embryonic development in sexually reproducing multicellular organisms is made possible through the process of gametogenesis and fertilization.
• Gametogenesis is the formation of sex cells or reproductive cells also known as gametes.
• Gametogenesis happens in primary sex organ called gonads.
• The male gonad is called testis while in female is ovary which both contain primordial germ cells.
• Primordial germ cells are the common origins of spermatozoa and oocytes, these cells are responsible for the production.
• Spermatogenesis is the formation of sperm cells located in the seminiferous tubules of male gonad.
• Seminiferous tubules are the site for germination, maturation, and transportation of the sperm cells within the male testes.
• The primordial germ cells produce cells which ultimately become sperm mother cells or spermatogonia.
• It is the most immature sperm cell originated from primordial sperm cell.
• Through growth phase (mitosis) the spermatogonia get converted into primary spermatocyte which are diploid cells (2n=46 chromosomes).
• Spermatocyte undergo meiotic cell division, initially the meiosis I results in the formation of secondary spermatocyte and through meiosis II they form spermatids.
• The spermatids are haploid (n=23 chromosomes) in nature and by process of spermiogenesis they get differentiated into cells called spermatozoa.
• Spermiogenesis is the transformation of spermatids into function spermatozoa.
• The spermatogenesis produced four haploid cells at the end of the process.
• Spermatozoa is the male mature sperm cells.
• Oogenesis is the formation of ovum located in the female gonad called ovary.
• Oogenesis happens inside the primordial germ cells and it start from oogonium, the immature female germ cell.
• Through mitosis the oogonium get converted into primary oocyte which are diploid cells (2n=46).
• Primary oocyte undergo meiotic cell division, first the meiosis I whixh results in the formation of secondary oocytes and the first polar body.
• Polar body is a small haploid cell that is formed concomitantly as an egg cell during oogenesis, but which does not have the ability to be fertilized.
• Meiosis II results in the formation of ootid which contain haploid cell (n=23 chromosomes), and formation of second polar bodies from primary polar body.
• During formation of oocytes, polar bodies will degenerate.
• The ootid will be converted into ovum, the mature egg cell.
• At the end of the process, oogenesis produced haploid cells or one ovum.