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chiasma

 
Dictionary: chi·as·ma   (kī-ăz') pronunciation also chi·asm
('ăz'əm)
n., pl., -ma·ta (-mə-tə), or -mas, also -asms.
  1. Anatomy. A crossing or intersection of two tracts, as of nerves or ligaments.
  2. Genetics. The point of contact between paired chromatids during meiosis, resulting in a cross-shaped configuration and representing the cytological manifestation of crossing over.

[Greek khīasma, cross-piece, from khīazein, to mark with an X, from khei, khī, chi (from the letter's shape).]

chiasmal chi·as'mal or chi·as'mic or chi'as·mat'ic (-măt'ĭk) adj.

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Biology Q&A: What are chiasmata?
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The site of "crossing over," where homologous chromosomes actually exchange material during the first round of meiosis, is known as a chiasma. The plural version is chiasmata.

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Pl. chiasmata [L., Gr.] chiasm; in genetics, the points at which members of a chromosome pair are in contact during the prophase of meiosis and because of which recombination, or crossing over, occurs on separation.

  • c. formation — the process by which a chiasma is formed; it is the cytological basis of genetic recombination, or crossing over.
  • c. syndrome — optic atrophy with bilateral hemianopia.
Wikipedia: Chiasma
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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.

Chiasma may also refer to:

  • The point where nerves or ligaments cross or intersect
  • The optic chiasm
  • Chiasma (genetics), the point where two chromatids are intertwined (interwoven) in a cell

 
 
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achiasmate (cell and molecular biology)
lamina terminalis (anatomy)
optic tract (neuroscience)

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