nounWord forms: plural-mas, -mata (-mətə) or -asms
1. cytology
the cross-shaped connection produced by the crossing over of pairing chromosomes during meiosis
2. anatomy
the crossing over of two parts or structures, such as the fibres of the optic nerves in the brain
Derived forms
chiasmal (chiˈasmal) or chiasmic (chiˈasmic)
adjective
Word origin
C19: from Greek khiasma wooden crosspiece, from khiazein to mark with an X, from khichi1
Examples of 'chiasmata' in a sentence
chiasmata
The frequency of interstitial and terminal chiasmata was more variable.
Flávia Roseli Baptista-Giacomelli, Maria Suely Pagliarini, Juliano Luiz de Almeida 2000, 'Freqüência, distribuição e terminalização de quiasmas em aveias hexaplóides (Avenasativa L.) Chiasma frequency, distribution and terminalization in hexaploid oats(Avena sativa L.)', Acta Scientiarum : Biological Scienceshttp://www.periodicos.uem.br/ojs/index.php/ActaSciBiolSci/article/view/2811. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
The average number of chiasmata per cell was 15.88.
Cândida H. T. Mendes 1950, 'Observações citológicas em Coffea: XVI - Microsporogênese em Coffea canephora Pierreex Froehner', Bragantiahttp://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87051950000400001. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
The frequency of total and terminal chiasmata decreased with endogamy.
Maria Fernanda Piffer Tomasi Baldez da Silva, Eraldo Ferreira Lopes, Maria Suely Pagliarini,Carlos Alberto Scapim 2007, 'Effects of endogamy on microsporogenesis in popcorn (Zea mays L.)', Crop Breeding and Applied Biotechnologyhttp://www.sbmp.org.br/cbab/siscbab/uploads/bd6b9df0-0dff-c345.pdf. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
The number of chiasmata per genome increases with an increase in the polyploid level.
J. J. Spies, C. H. Stirton 1982, 'Meiotic studies of some South African cultivars of Lantana camara (Verbenaceae)',Bothalia: African Biodiversity & Conservationhttps://abcjournal.org/index.php/abc/article/view/1148. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
During the first meiotic division, homologous chromosomes pair, recombine, and form chiasmata.
Yong-Hyun Shin, Youngsok Choi, Serpil Uckac Erdin, Svetlana A Yatsenko, MalgorzataKloc, Fang Yang, P Jeremy Wang, Marvin L Meistrich, Aleksandar Rajkovic 2010, 'Hormad1 mutation disrupts synaptonemal complex formation, recombination, and chromosomesegregation in mammalian meiosis.', PLoS Geneticshttp://europepmc.org/articles/PMC2973818?pdf=render. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Then, there are not bivalents, no chiasmata-achiasmata- as there are not four chromatids two of which resulted sister-chromatids.
Armando García-Velázquez 2008, 'Meiosis en mutantes desinápticos con restitución cromosómica en Rhoeo spathacea (Commelinaceae)Meiosis in desynaptic-chromosomal restitution mutants in Rhoeo spathacea (Commelinaceae)',Acta Agronómicahttp://www.scielo.org.co/scielo.php?script=sci_arttext&pid=S0120-28122008000300005. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Crossover recombination and the formation of chiasmata normally ensure the proper segregation of homologous chromosomes during the first meiotic division.
Needhi Bhalla, David J Wynne, Verena Jantsch, Abby F Dernburg 2008, 'ZHP-3 acts at crossovers to couple meiotic recombination with synaptonemal complexdisassembly and bivalent formation in C. elegans.', PLoS Geneticshttp://europepmc.org/articles/PMC2567099?pdf=render. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Chiasmata are essential for the accurate chromosome segregation and the generation of new combinations of parental alleles.
Adela Calvente, Juan Luis Santos, Julio S Rufas 2016, 'Do Exogenous DNA Double-Strand Breaks Change Incomplete Synapsis and Chiasma Localizationin the Grasshopper Stethophyma grossum?', PLoS ONEhttp://europepmc.org/articles/PMC5179137?pdf=render. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
The bivalents may present one, two or three chiasmata, but those with two terminalchiasmata were more frequent.
Flávia Roseli Baptista-Giacomelli, Maria Suely Pagliarini, Juliano Luiz de Almeida 2000, 'Freqüência, distribuição e terminalização de quiasmas em aveias hexaplóides (Avenasativa L.) Chiasma frequency, distribution and terminalization in hexaploid oats(Avena sativa L.)', Acta Scientiarum : Biological Scienceshttp://www.periodicos.uem.br/ojs/index.php/ActaSciBiolSci/article/view/2811. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
In addition, chiasmata also aid in proper segregation of homologous chromosomes and has a major impact on reproductive fitness.
Alphy John, Kavya Vinayan, Jishy Varghese 2016, 'Achiasmy: Male fruit flies are not ready to mix', Frontiers in Cell and Developmental Biologyhttp://journal.frontiersin.org/Journal/10.3389/fcell.2016.00075/full. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)