WordNet

complicated in structure; consisting of interconnected parts; "a complex set of variations based on a simple folk melody"; "a complex mass of diverse laws and customs"
a compound described in terms of the central atom to which other atoms are bound or coordinated (同)coordination_compound
a conceptual whole made up of complicated and related parts; "the complex of shopping malls, houses, and roads created a new town" (同)composite
(psychoanalysis) a combination of emotions and impulses that have been rejected from awareness but still influence a persons behavior

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『いくつかの部分から成る』,複合の,合成の / 『複雑な』,入りくんだ,こみいった(complicated) / 複合体,合成物 / コンプレックス,複合(抑圧されて心に残った複雑なしこり)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/01/18 05:03:54」(JST)

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A Homologous chromosomes (light blue) align and synapse together via transverse filaments (black lines) and longitudinal filaments (dark blue). Recombination nodules (gray ellipsoids) on the central region may help in completing recombination. Chromatin (red loops) is attached to its corresponding chromosome, extending from both sister chromatids. B Top: Set of tomato SCs. Chromatin “sheaths” visible around each SC. Bottom: Two tomato SCs with the chromatin removed, allowing kinetochores (“ball-like” structures) at centromeres to be revealed.

The synaptonemal complex is a protein structure that forms between homologous chromosomes (two pairs of sister chromatids) during meiosis and is thought to mediate chromosome pairing, synapsis, and recombination. It is now evident that the synaptonemal complex is not required for genetic recombination^{[citation needed]}. Research has shown that not only does it form after genetic recombination but mutant yeast cells unable to assemble a synaptonemal complex can still engage in the exchange of genetic information.^{[citation needed]} It is currently thought that the SC functions primarily as a scaffold to allow interacting chromatids to complete their crossover activities. The synaptonemal complex is a tripartite structure consisting of two parallel lateral regions and a central element.

Three specific components of the synaptonemal complex have been characterized: SC protein-1 (SYCP1), SC protein-2 (SYCP2), and SC protein-3 (SYCP3). In humans, the SYCP1 gene is on chromosome 1p13; the SYCP2 gene is on chromosome 20q13.33; and the gene for SYCP3 is on chromosome 12q.

The synaptonemal complex (SC) was described by Montrose J. Moses in 1956 in primary spermatocytes of crayfish and by D. Fawcett in spermatocytes of pigeon, cat and man. As seen with the electron microscope, the synaptonemal complex is formed by two "lateral elements", mainly formed by SYCP3 and secondarily by SYCP2, a "central element" that contains at least two additional proteins and the amino terminal region of SYCP1, and a "central region" spanned between the two lateral elements, that contains the "transverse filaments" composed mainly by the protein SYCP1.

The SCs can be seen with the light microscope using silver staining or with immunofluorescence techniques that label the proteins SYCP3 or SYCP2.

This "tripartite structure" is seen during the pachytene stage of the first meiotic prophase, both in males and in females during gametogenesis. Previous to the pachytene stage, during leptonema, the lateral elements begin to form and they initiate and complete their pairing during the zygotene stage. After pachynema ends, the SC usually becomes disassembled and can no longer be identified.

Formation of the SC usually reflects the pairing or "synapsis" of homologous chromosomes and may be used to probe the presence of pairing abnormalities in individuals carrying chromosomal abnormalities, either in number or in the chromosomal structure. The sex chromosomes in male mammals show only "partial synapsis" as they usually form only a short SC in the XY pair. The SC shows very little structural variability among eukaryotic organisms despite some significant protein differences. In many organisms the SC carries one or several "recombination nodules" associated to its central space. These nodules are thought to correspond to mature genetic recombination events or "crossovers".

In cell development the synaptonemal complex disappears during the late prophase of meiosis I.

One aspect of meiosis research (in genetics, molecular biology, and reproductive medicine) involving synaptonemal complexes is how they (or what they do) can be affected and damaged by chemical exposure, specifically by toxins like bisphenol A (an experiment at Harvard Medical School by Dr. Monica Colaiácovo, Ph.D., an associate professor of genetics, involved dosing C. elegans worms with that toxin and then verifying the results in mouse studies).^[1]

References

Moses MJ, Annu. Rev. Genet. 2:363-412 (1968.
Zickler D., Kleckner N., Annu. Rev. Genet. 33:603-754 (1999)
Karp G., Cell and Molecular Biology" 14:603-604 (2008)

External links

[1] - Synaptonemal complex

by 3D-Structured Illumination, photograph by Dr. Chung-Ju Rachel Wang University of California Berkeley, Department of Molecular and Cell Biology Berkeley, CA, USA, second place winner of the 2009 Olympus Bioscapes Digital Imaging Competition.

[2]
Kounetsova A. et al, Meiosis in Mice without a Synaptonemal Complex PLOS ONE (2011)

^ http://hms.harvard.edu/news/green-eggs-and-him

UpToDate Contents

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English Journal

PRDM9 interactions with other proteins provide a link between recombination hotspots and the chromosomal axis in meiosis.

Parvanov ED1,2, Tian H1, Billings T1, Saxl RL1, Spruce C1, Aithal R2, Krejci L3,4, Paigen K1, Petkov PM5.
Molecular biology of the cell.Mol Biol Cell.2016 Dec 8. pii: mbc.E16-09-0686. [Epub ahead of print]
In mammals, meiotic recombination occurs at 1-2 kb genomic regions termed hotspots, whose positions and activities are determined by PRDM9, a DNA-binding histone methyltransferase. We now show that the KRAB domain of PRDM9 forms complexes with additional proteins to allow hotspots to proceed into th
PMID 27932493

Arrest at the diplotene stage of meiotic prophase I is delayed by progesterone but is not required for primordial follicle formation in mice.

Dutta S1,2, Burks DM1, Pepling ME3.
Reproductive biology and endocrinology : RB&E.Reprod Biol Endocrinol.2016 Dec 5;14(1):82.
BACKGROUND: In mammalian females, reproductive capacity is determined by the size of the primordial follicle pool. During embryogenesis, oogonia divide mitotically but cytokinesis is incomplete so oogonia remain connected in germ cell cysts. Oogonia begin to enter meiosis at 13.5 days postcoitum in
PMID 27919266

Meiotic Centromere Coupling and Pairing Function by Two Separate Mechanisms in Saccharomyces cerevisiae.

Kurdzo EL1, Obeso D1, Chuong H1, Dawson DS2.
Genetics.Genetics.2016 Dec 2. pii: genetics.116.190264. [Epub ahead of print]
In meiosis I, chromosomes become paired with their homologous partners and then are pulled towards opposite poles of the spindle. In the budding yeast, Saccharomyces cerevisiae, in early meiotic prophase, centromeres are observed to associate in pairs in a homology-independent manner, a process call
PMID 27913618