chiasma

chiasma
SYN: chiasm. [G. c., two crossing lines, fr. the letter chi, 3]
- c. opticum [TA] SYN: optic chiasm.
- c. tendinum [TA] SYN: tendinous chiasm of the digital tendons.

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chi·as·ma kī-'az-mə, kē- n, pl -ma·ta -mət-ə
1) an anatomical intersection or decussation see OPTIC CHIASMA
2) a cross-shaped configuration of paired chromatids visible in the diplotene of meiotic prophase and considered the cytological equivalent of genetic crossing-over
chi·as·mat·ic .kī-əz-'mat-ik, .kē- adj

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n. (pl. chiasmata)
1. (in genetics) the point at which homologous chromosomes remain in contact after they have started to separate in the first division of meiosis. Chiasmata occur from the end of prophase to anaphase and represent the point at which mutual exchange of genetic material takes place (see crossing over).

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chi·as·ma (ki-azґmə) pl. chiasґmata [L., from Gr. “a cross, crosspiece,” from the shape of the letter chi (X)] 1. an anatomical term for a decussation or X-shaped crossing, such as of nerves. 2. a point where pairs of homologous chromatids remain in contact during late prophase to anaphase of meiosis I, indicating where an exchange of homologous segments has taken place between nonsister chromatids by recombination.

Medical dictionary. 2011.

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  • chiasma — [ kjasma ] n. m. • 1863; mot gr.→ chiasme ♦ Anat. Entrecroisement de nerfs ou de chromatides. Le chiasma optique. Adj. CHIASMATIQUE . ● chiasma nom masculin Croisement des nerfs optiques droit et gauche dans l encéphale. chiasma n. m. ANAT… …   Encyclopédie Universelle

  • chiasmă — CHIÁSMĂ, chiasme, s.f. Formaţie nervoasă din interiorul craniului, alcătuită din încrucişarea parţială a fibrelor nervilor optici. – Din fr. chiasma. Trimis de valeriu, 03.03.2003. Sursa: DEX 98  chiásmă (anat., biol.) s. f. (sil. chi as ), g. d …   Dicționar Român

  • chiasma — [kī az′mə] n. pl. chiasmata [kī az′mətə] [ModL < Gr chiasma, a crosspiece < chiasmos, placing crosswise < chiazein, to mark with a chi (χ)] 1. a crossing or intersection of the optic nerves in the hypothalamus of the brain 2. a point of… …   English World dictionary

  • chiasma — chiasma. См. перекрест. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Chiasma — (griech.), die Kreuzung von Nervenfaserbündeln, s. Tafel »Auge des Menschen«, mit Text …   Meyers Großes Konversations-Lexikon

  • Chiasma — (grch.), Kreuzung; C. nervōrum opticōrum, Sehnervenkreuzung im Gehirn …   Kleines Konversations-Lexikon

  • Chiasma — Chiasma, durch ⇒ crossing over – den Austauschvorgang zwischen homologen Chromatiden in der Prophase der Meiose – entstandene Kreuzfigur, die im Diplotän, wenn die auseinander weichenden homologen Chromosomen noch an den Chiasmen zusammenhängen,… …   Deutsch wörterbuch der biologie

  • Chiasma — Chiasm Chi asm (k[imac] [a^]z m), ||Chiasma Chi*as ma (k[ i]*[a^]z m[.a]), n. [NL. chiasma, fr. Gr. chi asma two lines placed crosswise, fr. ? to mark with a [chi].] (Anat.) A commissure; an intersection or crossing of two tracts; especially, the …   The Collaborative International Dictionary of English

  • Chiasma — The term chiasma comes from the Greek χίασμα, which is related to the Greek letter Χ and means crossing . It has a number of related meanings in biology. The plural is chiasmata .* It is sometimes used to refer to the optic chiasm. * More… …   Wikipedia

  • Chiasma — Ein Chiasma (gr. χίασμα chíasma „Kreuzung“, nach dem griechischen Buchstaben Χ, Chi) ist eine Überkreuzung zweier Chromatiden homologer Chromosomen. In der Prophase I der Meiose kommt es zur Verkürzung der Chromosomen, so dass diese… …   Deutsch Wikipedia

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