5. Gametogenesis

5.1 Definition

·       Gametogenesis is the biological process by which haploid gametes (sperm and ova) are formed from diploid germ cells through meiotic cell division and cellular differentiation.

o   In males, this process is called spermatogenesis.

o   In females, it is called oogenesis.

·       Begins in fetal life for females; at puberty for males.

·       The ultimate goal of gametogenesis is to produce mature, functional gametes capable of fertilization, restoring the diploid chromosome number in the resulting zygote.

5.2      Origin of Germ Cells

§  Primordial germ cells (PGCs) originate in the yolk sac endoderm during early embryonic development.

§  They migrate to the developing gonadal ridge (future testes or ovaries) by the 6th week of gestation.

§  Once in the gonads, these cells multiply by mitosis and later enter meiosis to form gametes.

5.3      Common Features

  • Both involve meiosis → haploid gametes.
  • Begin from primordial germ cells (PGCs).
  • Require support from surrounding somatic cells:
    • Sertoli cells in testes
    • Granulosa cells in ovary