Gametogenesis and Fertilization in Mammals

Gametogenesis and fertilization represent the continuum of processes that culminate in the formation of a zygote, a unique combination of genetic traits of two parents. Mammalian gametogenesis results from meiotic divisions of specialized germ cells within the gonads. Fertilization and the development of the embryo from the zygote occur within the female reproductive organs.

In males the diploid germ cell, or spermatogonium, undergoes two divisions of meiosis and differentiates into four haploid sperm. After puberty, gametogenesis in the male is continuous within the testes, and the mature sperm are deposited in the female tract to fertilize the secondary oocyte.

In females the diploid oogonium undergoes two divisions of meiosis, but only one of the four resulting haploid nuclei will develop into a fully differentiated ovum; the other three nuclei become polar bodies and degenerate. The meiotic divisions of oogenesis begin at birth and proceed in discontinuous stages that include long intervals between nuclear divisions. The second meiotic division occurs only after fertilization by sperm; therefore, gametogenesis in the female is dependent on fertilization for completion.

Gametogenesis and Fertilization Home Page
Gametogenesis and Fertilization in Angiosperms
Gametogenesis and Fertilization in Mammals
Laboratory Exploration: Pollen Tube Germination
Supplemental Activities on Gametogenesis and Fertilization