Germ cells

haploid female reproductive cell or gamete

A gamete ( ), reproductive cell, or sex cell, is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878.

thumb|300px|Spores produced in a sporic life cycle thumb|300px|Fresh snow partially covers rough-stalked feather-moss (Bryopsida|Brachythecium rutabulum), growing on a thinned hybrid black poplar (Populus x canadensis). The last stage of the moss lifecycle is shown, where the [[sporophytes are visible before dispersion of their spores: the calyptra (1) is still attached to the capsule (3). The tops of the gametophytes (2) can be discerned as well. Inset shows the surrounding, black poplars growing on sandy loam on the bank of a kolk, with the detail area marked.]]

Sperm (: sperm or sperms) is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring (excluding, in most cases, mitochondrial DNA). Animals produce motile sperm with a tail known as a flagellum, which are known as spermatozoa, while some red algae and fungi produce non-motile sperm cells, known as spermatia. Flowering plants contain non-motile sperm inside pollen, while some more ba

Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes 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.

thumb|Different forms of anisogamy: A) anisogamy of motile cells, B) oogamy ([[egg cell and sperm cell), C) anisogamy of non-motile cells (egg cell and spermatia).|283x283px]]

[[File:Isogamy.svg|thumb|Different forms of isogamy:

An oocyte (, oöcyte, or ovocyte) is a female germ cell involved in sexual reproduction. An oocyte is an immature ovum, an immature egg cell produced in a female fetus in the ovary during gametogenesis. During oogenesis, the oogonia become primary oocytes. An oocyte is a form of genetic material that can be collected for cryopreservation.

gamete-producing cell

A spermatogonium (plural: spermatogonia) is an undifferentiated male germ cell. Spermatogonia undergo spermatogenesis to form mature spermatozoa in the seminiferous tubules of the testicles.

An oogonium (: oogonia) is a small diploid cell which, upon maturation, forms a primordial follicle in a female fetus or the female (haploid or diploid) gametangium of certain thallophytes.

thumb|Oogamy in animals: small, motile sperm on the surface of an ovum

small haploid cell that is formed concomitantly as an egg cell during oogenesis, but which generally does not have the ability to be fertilized

thumb|Light micrograph of a whole-mount slide of gametangia of [[Equisetum]] A gametangium (: gametangia) is a sex organ or cell in which gametes are produced that is found in many multicellular protists, algae, fungi, and the gametophytes of plants. In contrast to gametogenesis in animals, a gametangium is a haploid structure and formation of gametes does not involve meiosis.

right|thumb|500px|Spermatogenesis as the cells progress from spermatogium, to primary spermatocytes, to secondary spermatocytes, to [[spermatids and to sperm.]]

The spermatid is the haploid male gametid that results from division of secondary spermatocytes. As a result of meiosis, each spermatid contains only half of the genetic material present in the original primary spermatocyte.

thumb|right|upright=1.2|alt=Microscope view of a transparent sac (ascus) holding four oval, golden-brown spores. The spores are covered with a raised, net-like pattern that looks like a mosaic of tiny scales.|Four ornamented ascospores of the Oregon white truffle (Tuber oregonense) inside a single ascus. Each [[ellipsoid spore shows the typical honey-gold colour and ornamentation of polygonal pits bordered by low ridges.]] In fungi, an ascospore is the sexual spore formed inside an ascus, a sac-like cell. Asci define the division Ascomycota, the largest and most diverse division of fungi. Afte

thumb|400px|Scheme showing analogies in the process of maturation of the ovum and the development of the spermatids.A gametocyte is a eukaryotic germ cell that divides by mitosis into other gametocytes or by meiosis into gametids during gametogenesis. Male gametocytes are called spermatocytes, and female gametocytes are called oocytes.

Although the process is similar in many animals, this article will deal exclusively with human folliculogenesis. thumb|right|320px|Order of changes in ovary.1 - Menstruation2 - Developing follicle3 - Mature follicle4 - Ovulation5 - Corpus luteum6 - Deterioration of corpus luteum In biology, folliculogenesis is the maturation of the ovarian follicle, a densely packed shell of somatic cells that contains an immature oocyte. Folliculogenesis describes the progression of a number of small primordial follicles into large preovulatory follicles that occurs in part during the menstrual cycle.

thumb|Cormlets of Watsonia meriana, an example of [[apomixis]] thumb|Clathria tuberosa, an example of a sponge that can grow indefinitely from somatic tissue and reconstitute itself from totipotent separated somatic cells In biology and genetics, the germline is the population of a multicellular organism's cells that develop into germ cells. In other words, they are the cells that form gametes (eggs and sperm), which can come together to form a zygote. They differentiate in the gonads from primordial germ cells into gametogonia, which develop into gametocytes, which develop into the final game

thumb|right|Gram stain of Candida albicans from a vaginal swab, showing hyphae, and chlamydospores, which are 2–4 μm in diameter. A chlamydospore is the thick-walled large resting spore of several kinds of fungi, including Ascomycota such as Candida, Basidiomycota such as Panus, and various Mortierellales species. It is the life-stage which survives in unfavourable conditions, such as dry or hot seasons. Fusarium oxysporum which causes the plant disease Fusarium wilt is one which forms chlamydospores in response to stresses like nutrient depletion. Mycelia of the pathogen can survive in this m

thumb|Two-celled teliospore of Gymnosporangium globosum Teliospore (sometimes called teleutospore) is the thick-walled resting spore of some fungi (rusts and smuts), from which the basidium arises.

Capacitation is a process sperm must undergo to prepare to fertilize an egg. This is a process that mature spermatozoa undergo after entering the oviduct and uterus of the female reproductive tract. Sperm must undergo capacitation and the acrosome reaction to be able to penetrate through the outer layers of an oocyte, namely the cumulus ooporus and the zona pellucida. Capacitation results in hyperactivation of sperm motility, with the acrosome and cortical reaction following this. Compounds such as heparin and progesterone can be used to induce capacitation.

biological concept

Gametogamy is sexual fusion – copulation or fertlization – of two single-celled gametes of different sex and the union of their gamete nuclei (and corresponding extranuclear structures) giving the zygote nucleus, as well as whole zygotic content.

biological process that prevents polyspermy

thumb|right|Diagram of vitellogenesis in the digenean [[Crepidostomum metoecus. GER: granular endoplasmic reticulum; L: lipid droplet; M: mitochondrion; N: nucleus; Nl: nucleolus; SG: shell globule; SGC: shell globule cluster.]]

Gonocytes are the precursors of spermatogonia that differentiate in the testis from primordial germ cells around week 7 of embryonic development and exist up until the postnatal period, when they become spermatogonia. Germ cells operate as vehicles of inheritance by transferring genetic and epigenetic information from one generation to the next. Male fertility is centered around continual spermatogonia which is dependent upon a high stem cell population. Thus, the function and quality of a differentiated sperm cell is dependent upon the capacity of its originating spermatogonial stem cell (SSC

thumb|Urediniospores of 11 Milesina (fungus)|Milesina species. a [[Milesina blechni on Struthiopteris spicant b Milesina blechni on Struthiopteris spicant, cracked spore with released plasma, germ pores scattered c Milesina carpatica on Dryopteris filix-mas d Milesina exigua on Polystichum braunii, smooth surface e Milesina exigua on Polystichum braunii, smooth surface, plasma-free spore, germ pores bipolar f Milesina feurichii on Asplenium septentrionale with smooth areas on surface g Milesina feurichii on Asplenium septentrionale, cracked plasma-free spore, germ pores scattered h Milesina kr