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Gametogenesis is a biology process by which diploid or haploid undergo cell division and differentiation to form mature haploid . Depending on the biological life cycle of the organism, gametogenesis occurs by meiosis division of diploid into various gametes, or by mitosis. For example, plants produce gametes through mitosis in gametophytes. The gametophytes grow from haploid spores after sporic meiosis. The existence of a multicellular, haploid phase in the life cycle between meiosis and gametogenesis is also referred to as alternation of generations.
It is the biological process of gametogenesis during which cells that are haploid or diploid divide to create other cells. It can take place either through mitotic or meiotic division of diploid gametocytes into different cells depending on an organism's biological life cycle. For instance, gametophytes in plants undergo mitosis to produce gametes. Both male and female have different forms.
| gametocytogenesis (mitosis) | |
| [[gametidogenesis]] ([[meiosis]] I) | |
| gametidogenesis (meiosis II) | |
| + !spermatogenesis !oogenesis | |
| Begins at puberty | starts before birth |
| Have equal division of cells | unequal division of cells |
| produces four functional sperm from each primary spermatocyte | produces one functional ovum and three polar bodies from each primary oocyte |
| Takes place in the testis | takes place in the ovaries |
| Regulated by testerone and Follicle Stimulating Hormone | regulated by oestrogen, progesterone, Leutenizing Hormone |
| It is continuous | stops at some point in life |
| Produces millions of sperms daily | produces one ovum per menstrual cycle |
In angiosperms the division of a generative cell into two, sperm nuclei, resulting in the production male gametes (always two), which develop inside the pollen grain (in 30% of species) or the pollen tube (in 70% of species), respectively, of the plant. This may happen before pollination and the development of the pollen tube, depending on the species, or while the pollen is still forming in the anther (pollen is tricellular) (pollen bicellular in the anther and in the stigma). Inside the embryo sac of the ovule, the female gamete is created.
Although meiosis is a crucial component of gametogenesis, its function in adaptation is still unknown. In sexually reproducing organisms, it is a type of cell division that results in fewer chromosomes being present in gametes.
HOMOLOGY EFFECTS
There are two key differences between mammalian and plant gametogenesis. First, there is no predetermined germline in plants. Male or female gametophyte-producing cells diverge from the reproductive meristem, a totipotent clump of developing cells in the adult plant that creates all the flower's features (both sexual and asexual structures). Second, meiosis is followed by mitotic divisions and differentiation to create the gametes. In plants, sister, non-gametic cells are connected to the female gametes (the egg cell and the central cell) (the synergids and the antipodal cells). The haploid microspore passes through a mitosis to create a vegetative and generative cell during male gametogenesis. The generative cell undergoes a second mitotic division, resulting in the creation of two.
Premeiotic, post meiotic, pre mitotic, or postmitotic events are all possibilities if imprints are created during male and female gametogenesis. However, if only one of the daughter cells receives parental imprints following mitosis, this would result in two functionally different female gametes or two functionally different sperm cells. Demethylation is seen in the pollen grain following the second meiosis and before to the generative cell's mitosis, as was discussed in the section before this one. Along with pollen differentiation, various structural and compositional DNA alterations also occur. These modifications are potential steps for the genome-wide erasure and/or reprogramming of the imprinting that happens in animals. During the growth of sperm cells, the male DNA is extensively demethylated in plants, whereas the converse is true in animals.
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