chiasma definition | Dictionary.com

chi⋅as⋅ma

[kahy-az-muh]

–noun, plural -mas, -ma⋅ta [-muh-tuh]

1.	Anatomy. a crossing or decussation, as that of the optic nerves at the base of the brain.

2.	Cell Biology. a point of overlap of paired chromatids at which fusion and exchange of genetic material take place during prophase of meiosis.

Also, chi⋅asm [kahy-az-uh

Origin:
1830–40; < Gk: crosspiece of wood, cross-bandage, equiv. to chi chi ¹ + -asma n. suffix

Dictionary.com Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.
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chi·as·ma (kī-āz'mə) Pronunciation Key
n. pl. chi·as·ma·ta (-mə-tə) or chi·as·mas also chi·asms

Anatomy A crossing or intersection of two tracts, as of nerves or ligaments.
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).]

chi·as'mal, chi·as'mic, chi'as·mat'ic (-māt'ĭk) adj.

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2006 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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chiasma
noun
an intersection or crossing of two tracts in the form of the letter X

WordNet® 3.0, © 2006 by Princeton University.
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