Gametogenesis

GAMETOGENESIS

SCHEME OF GAMETOGENESIS

GAMETOGENESIS

IN ANIMALS IN SEED PLANT

Spermatogenesis Oogenesis Microsporogenesis Megasporogenesis

GAMETOGENESIS

Gametogenesis is the formation of gamete cells.

GAMETOGENESIS

IN ANIMALS IN SEED PLANT

GAMETOGENESIS IN ANIMALS

Gametogenesis in animals happens in male and female sex organs. In animal cells, gametogenesis always happens in the body of diploid individuals through meiosis process. In male animals gametogenesis happens in the testis while in female animals gametogenesis happens in the ovary.

GAMETOGENESIS IN ANIMALS

SPERMATOGENESIS

OOGENESIS

Spermatogenesis

Spermatogenesis is the formation of male gamete cells (spermatozoa). This process happens in the testis.

In the testis there is a part called tubulus seminiferus. In this part primordium cells that have diploid property are found. Primordium cells will undergo mitosis fission frequently. One of fission results is the formation of spermatogonium.

Spermatogenesis

Spermatogenesis begins with spermatogonium that has diploid property (2n) to split by means of mitosis, producing primary spermatocyte that has diploid property (2n). Then the primary spermatocyte splits by means of meiosis. In meiosis I two secondary spematocyte that have haploid property (n) are produced and in the end of meiosis I four spermatids that have haploid property (n) are produced. Finally, the spermatid undergo differentiation and change into spermatozoa.

SpermatogenesisThus, in

spermatogenesis four functional spermatozoa that have haploid property (n) are produced.

Oogenesis

Oogenesis is the formation of female gametes (ova). This process happens in the ovary in which there is a cell, that is oogonium.

Oogenesis

Oogenesis begins with oogonium having diploid property (2n) that splits by means of mitosis producing primary oocyte that has diploid property (2n). Then the primary oocyte splits by means of meiosis. The product of meiosis I is a secondary oocyte and a primary pole body. These two cells have unequal sizes, the body of primary pole has a smaller size compared to the secondary oocyte. Then these two kinds of cell continue their meiosis fission so the product of meiosis I is one ootid and three secondary pole bodies. The secondary pole bodies undergo degeneration, so finally they die, while the ootid undergoes development into an ovum.

OogenesisSo, in

oogenesis one functional ovum that has haploid property (n) and three non functional polar bodies are produced.

GAMETOGENESIS IN SEED PLANTIn plants, meiosis also plays an important role

in gamete cell formation. In seed plants, meiosis happens in the anther and embryo, while in moss it happens in the sporogonium and in ferns meiosis happens in the sporangium.GAMETOGENESIS IN SEED PLANT

MICROSPOROGENESIS

MEGASPOROGENESIS

MicrosporogenesisMicrosporogenesis is the

formation of male gametes (pollen grains). This process happen in the anther.

In the anther, there are pollen chambers. In each chamber there is microsporocyte that has diploid property (2n). The microsporocyte then splits by means of meiosis producing four microspores. Each microspore develops into an adult microspore (polen grains). Each polen grain contains one tubular cell and one generative nucleus that is ready to fertilize.

Megasporogenesis

Megasporogenesis is the formation of female gametes (ova). This process happens in the ovary.

Megasporogenesis

In the ovary, there is megasporocyte that has diploid property (2n). The megasporocyte then splits by means of meiosis producing four haploid cells, but only one develops into a megaspore, while the three cells undergo degeneration. Then the nucleus of megaspore splits into two, the two split again into four , and the four split again into eight haploid nuclei. Then from those eight haploid nuclei, three nuclei lie near the microphyle, two of them as synergid cells and one in the middle (flanked by the synergid cells) as ovum. Three other nuclei lie in different places with the microphyle as the antipode. Two nuclei join in the middle as a secondary embryonic nucleus.