gametogenesis - process by which gametes are produced
spermatogenesis is the production of sperm in the seminiferous tubules
diagram on spermatogenesis
- spermatogonium undergoes mitosis to form spermatogonia. This is the multiplication phase
- spermatogonia undergoes cell growth to become the primary spermatocyte
- the primary spermatocyte undergoes meiosis I to become two haploid secondary spermatocytes
- the secondary spermatocytes undergo meiosis II to become four haploid spermatids
- the four haploid spermatids then undergoes cell differntiation to become four haploid spermatozoa
Functions of sperm
- deliver haploid nucleus with set of paternal chromosome to female gametes
- restore diploid number
- increase genetic variation
- stimulate meiosis II in the secondary oocyte
- determine gender of the next generation
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Oogenesis is the production of eggs
diagram of oogenesis
- oogonia undergoes mitosis to form primary oocytes
- each month after puberty one diploid primary oocyte undergoes meiosis I to form a haploid secondary oocyte and the first polar body which degenerates
- the secondary oocyte then will undergo meiosis II ONLY when it is fertilized by a sperm
- when it is fertilized by a sperm the haploid secondary oocyte will complete meiosis II to form a second polar body which degenerates and a fertilized ovum (zygote)
NB the nucleus divides but it is unequal which results in one large egg that may become a ovum and the polar body which contains a nucleus and verry little cytoplasm
Cell that is released from the ovary is the secondary oocyte and it has not completed meiosis. fertilization stimulates the completion of meiosis II followed by unequal cytokinesis to form tiny second polar body and the ovum
Function of ooctye
- provide haploid nucleus with set of maternal chromosome
- increase genetic variation
- provide energy supple for developing embryo
