Gametogenese

Gametogenese, also called gametogenesis, is the biological process by which primitive germ cells develop into mature gametes. It involves initial mitotic proliferation of germ cells, followed by meiotic divisions that reduce the chromosome number by half, and subsequent cellular differentiation to form functional sperm or eggs. The process generates haploid gametes and introduces genetic diversity through recombination during meiosis.

In males, the process is called spermatogenesis and occurs in the seminiferous tubules of the testes. Spermatogonial stem cells divide mitotically to produce spermatocytes, which enter meiosis I to form secondary spermatocytes and then meiosis II to yield haploid spermatids. Spermiogenesis then transforms these round spermatids into mature spermatozoa with distinctive heads, midpieces, and tails. Spermatogenesis is a continuous process that begins at puberty and proceeds throughout adulthood, regulated by hormones such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH), with testosterone supporting germ cell development.

In females, the process is oogenesis and occurs in the ovaries. Oogenesis begins before birth, with oogonia differentiating into primary oocytes that arrest in prophase I. At puberty, the menstrual cycle periodically resumes meiosis for selected primary oocytes, which complete meiosis I to form a secondary oocyte and a first polar body. Meiosis II is typically arrested at metaphase II and only completes if fertilization occurs, yielding an ovum and a second polar body. Oogenesis produces a finite number of eggs over the female reproductive lifespan, with timing and efficiency influenced by hormonal cycles and age.

Gametogenesis is essential for sexual reproduction, enabling genetic variation and species propagation.