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Spermatogenesis - It starts in males at the age of puberty due to a significant increase in the secretion of Gonadotropin-Releasing Hormone (GRH).

Oogenesis It is initiated in females during the embryonic development stage when a couple of oogonia are formed within each fetal ovary. No more oogonia are formed or added after birth.

Spermatogenesis is the process of formation of haploid sperms from a diploid stem cell known as spermatogonium. The process occurs inside the seminiferous tubules in the testis. The entire process takes about 70 days. Oogenesis is the process of formation of the ovum. The process occurs in the ovaries of the female. One oogonium produces a single ovum.