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chiasma

 - 4 dictionary results

chi⋅as⋅ma

  [kahy-az-muh]
Use chiasma in a Sentence
–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-uhm] .

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

Related forms:
chi⋅as⋅mal, chi⋅as⋅mic, chi⋅as⋅mat⋅ic  [kahy-az-mat-ik] , adjective
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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chi·as·ma   (kī-āz'mə)   
n.   pl. chi·as·ma·ta (-mə-tə) or chi·as·mas also chi·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).]
chi·as'mal, chi·as'mic, chi'as·mat'ic (-māt'ĭk) adj.
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Medical Dictionary

Main Entry: chi·as·ma
Pronunciation: kI-'az-m&, kE-
Function: noun
Inflected Form: plural chi·as·ma·ta /-m&t-&/
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 /"kI-&z-'mat-ik, "kE-/ adjective
Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.
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Medical Dictionary

chiasma chi·as·ma (kī-āz'mə) or chi·asm (kī'āz'əm)
n. pl. or chi·as·mas, chi·as·ma·ta (-mə-tə), chi·as·ms

  1. A crossing or intersection of two tracts, as of nerves or ligaments.

  2. The point of contact between paired chromatids during meiosis, resulting in a cross-shaped configuration and representing the cytological manifestation of crossing over.

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

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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