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the development and maturation of sex cells through meiosis

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/03/10 19:55:37」(JST)

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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 mitotic division of haploid gametogenous cells. 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.

In animalsEdit

Scheme showing analogies in the process of maturation of the ovum and the development of the spermatids, following their individual pathways. The oocytes and spermatocytes are both gametocytes. Ova and spermatids are complete gametes. In reality, the first polar body typically dies without dividing.

Animals produce gametes directly through meiosis in organs called gonads (testicles in males and ovaries in females). Males and females of a species that reproduces sexually have different forms of gametogenesis

spermatogenesis (male)
oogenesis (female)

StagesEdit

However, before turning into gametogonia, the embryonic development of gametes is the same in males and females.

Common pathEdit

Gametogonia are usually seen as the initial stage of gametogenesis. However, gametogonia are themselves successors of primordial germ cells. During early embryonic development, primordial germ cells (PGCs) from the dorsal endoderm of the yolk sac migrate along the hindgut to the gonadal ridge. They multiply by mitosis, and, once they have reached the gonadal ridge in the late embryonic stage, are referred to as gametogonia. Once the germ cells have developed into gametogonia, they are no longer the same between males and females.

Individual pathEdit

From gametogonia, male and female gametes develop differently - males by spermatogenesis and females by oogenesis. However, by convention, the following pattern is common for both:

Cell type	ploidy/chromosomes in humans	DNA copy number/chromatids in human^{[Note 1]}	Process
gametogonium	diploid (2N)/46	2C before replication, 4C after / 46 before, 46 X 2 after	gametocytogenesis (mitosis)
primary gametocyte	diploid (2N)/46	2C before replication, 4C after / 46 before, 46 X 2 after	gametidogenesis (meiosis I)
secondary gametocyte	haploid (N)/23	2C / 46	gametidogenesis (meiosis II)
gametid	haploid (N)/23	C / 23
gamete	haploid (N)/23	C / 23

In gametangiaEdit

Fungi, algae, and primitive plants form specialized haploid structures called gametangia, where gametes are produced through mitosis. In some fungi, such as the Zygomycota, the gametangia are single cells, situated on the ends of hyphae, which act as gametes by fusing into a zygote. More typically, gametangia are multicellular structures that differentiate into male and female organs:

antheridium (male)
archegonium (female)

In flowering plantsEdit

In flowering plants, the male gamete is produced inside the pollen grain through the division of a generative cell into two sperm nuclei. Depending on the species, this can occur while the pollen forms in the anther or after pollination and growth of the pollen tube. The female gamete is produced inside the embryo sac of the ovule.

NotesEdit

^ Sources are mixed when using this system of numbering. Some sources use the chromatid number when writing "n" rather than the ploidy number. Hence gametogonium and primary gametocyte would be "4n" rather than "2n" with "4c" for copies. The system used below has been determined by wikipedia consensus and should not necessarily be used as the definitive source on the issue.

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1. 筋強直性ジストロフィー：治療と予後myotonic dystrophy treatment and prognosis [show details]
…transmission of the mutated allele . Disease-causing DM1 alleles may expand in length during gametogenesis, resulting in the transmission of longer CTG repeats that may be associated with earlier onset …
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…in patients with BWS, the maternal copy of the Beckwith-Wiedemann (BW) gene is silenced during gametogenesis and only the paternal copy is expressed. As a result, offspring with BWS receive a mutation passed…
3. 遺伝学：用語集genetics glossary of terms [show details]
…expression of a gene. Epigenetic changes may be stable in an individual, but may be reversed during gametogenesis or development. DNA methylation and histone acetylation are common epigenetic changes. Epigenetic…
4. 単一遺伝子疾患（メンデル遺伝病とそれ以外の遺伝病）の遺伝パターンinheritance patterns of monogenic disorders mendelian and non mendelian [show details]
…to arise through epigenetic modification of DNA that takes place in the ova and sperm during gametogenesis (before fertilization). Genes that are inactivated (silenced) in the female line are said to be…
5. 妊娠中のたばこ製品の使用：妊娠と新生児への影響cigarette and tobacco products in pregnancy impact on pregnancy and the neonate [show details]
… nitrosamines, and aromatic amines, appear to accelerate follicular depletion and may impede gametogenesis . A meta-analysis of 12 studies reported the overall odds ratio (OR) for risk of infertility…

English Journal

Gonadal transcriptomic analysis and identification of candidate sex-related genes in Mesocentrotus nudus.

Sun ZH, Zhang J, Zhang WJ, Chang YQ.
Gene. 2019 May;698()72-81.
The edible sea urchin, Mesocentrotus nudus, is both an economically important mariculture species and an excellent model for studying reproductive development. The gonads are the only edible parts of sea urchins and increasing market demand for high-quality gonads has prompted increasing amounts of
PMID 30825598

Stem Leydig cell regeneration in the adult rat testis is inhibited after a short-term triphenyltin exposure.

Ni C, Fang Y, Chen X, Wu K, Li H, Wang Y, Zhenkun L, Lian Q, Ge RS.
Toxicology letters. 2019 May;306()80-89.
Triphenyltin (TPT) is an organotin compound and may be an endocrine disruptor, impairing the male reproductive system. However, the effect of short-term TPT exposure on stem Leydig cell regeneration later on remains unknown. Here, we show that TPT affects stem Leydig cell regeneration in the adult r
PMID 30772500

Expression pattern of heat shock protein 90AB (HSP90AB) and stress-inducible protein 1 (Stip1) during spermatogenesis of mudskipper Boleophthalmus pectinirostris.

Du C, Han YL, Hou CC, Zhu JQ.
Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology. 2019 May;231()42-51.
Heat shock protein 90 (HSP90), which functions as a molecular chaperone, plays an important role in reproduction and cellular defense. Among the HSP90 family, HSP90AB is an important isoform. Stress-inducible protein 1 (Stip1) acts as a co-chaperone that mediates interactions with HSP90 and appears
PMID 30735774

Japanese Journal

生殖幹細胞からの配偶子形成 (第1土曜特集生殖医学・医療の最前線) -- (生殖医学研究の最前線)

高井泰
医学のあゆみ 249(1), 61-67, 2014-04-05
NAID 40020033779

Multiple BiP Genes of Arabidopsis thaliana are Required for Male Gametogenesis and Pollen Competitiveness (Special Focus Issue : Plant Endomembranes)

Maruyama Daisuke,Sugiyama Tomoyuki,Endo Toshiya [他]
Plant and cell physiology 55(4), 801-810, 2014-04
NAID 40020302117

Gibberellic acid-mediated male sterility during gametogenesis of <I>Brassica campestris</I> L.

Kumar Girjesh,Dwivedi Kshama
Chromosome Botany 9(3), 59-63, 2014
The present work was done to elucidate the impact of gibberellic acid (GA3) on male meiosis of <I>Brassica campestris</I> L. with an aim to study its cytological peculiarities. Microsporog …
NAID 130004691254

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