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 (kī-ăz′mə) also chi·asm (kī′ăz′əm)
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 (-măt′ĭk) adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(kaɪˈæzmə) or


n, pl -mas, -mata (-mətə) or -asms
1. (Genetics) cytology the cross-shaped connection produced by the crossing over of pairing chromosomes during meiosis
2. (Anatomy) anatomy the crossing over of two parts or structures, such as the fibres of the optic nerves in the brain
[C19: from Greek khiasma wooden crosspiece, from khiazein to mark with an X, from khi chi1]
chiˈasmal, chiˈasmic adj
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(kaɪˈæz mə)

also chi•asm

(ˈkaɪ æz əm)

n., pl. -as•mas, -as•ma•ta (-ˈæz mə tə) also -asms.
1. Anat. a crossing or decussation. Compare optic chiasma.
2. a point of overlap of paired chromatids at which fusion and exchange of genetic material take place during prophase of meiosis.
[1830–40; < Greek: crosspiece of wood, cross-bandage =chi chi + -asma n. suffix]
chi•as′mal, chi•as′mic, chi`as•mat′ic (-ˈmæt ɪk) adj.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.chiasma - an intersection or crossing of two tracts in the form of the letter X
anatomical structure, bodily structure, body structure, complex body part, structure - a particular complex anatomical part of a living thing; "he has good bone structure"
chiasma opticum, optic chiasm, optic chiasma - the crossing of the optic nerves from the two eyes at the base of the brain
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.


, chiasma
n. quiasma.
1. cruzamiento de dos vías o conductos;
2. punto de cruzamiento de las fibras de los nervios ópticos.
English-Spanish Medical Dictionary © Farlex 2012
References in periodicals archive ?
Chiasma ended the second quarter with cash, cash equivalents and marketable securities of $58.1 million.
A yeast two-hybrid screen for SYP-3 interactors identifies SYP-4, a component required for synaptonemal complex assembly and chiasma formation in Caenorhabditis elegans meiosis.
Pituitary gland height neurohypophysis brightness or ectopia, an undescended posterior lobe, infundibulum morphology, absence of corpus callosum and of septum pellucidum, optic nerve and chiasma, holoprosencephaly, schizencephaly, cerebellar hypoplasia, absence of fornix and presence of Chiari malformation should be assessed with imaging (66).
It has its neural basis in the lower frontal hypothalamus, situated above the optic chiasma. [3] These suprachiasmatic nuclei produce a cyclic oscillation with a period of 24 h.
Rather, it is a question of a chiasma between the two orders of signs" (2001, 61).
KEY: Anterior (A); Posterior (P); Medial (M); Lateral (L); Optic Nerve (ON); Optic Chiasma (Ch); Internai Carotid Artery (ICA); Intersinus Septum (IS); Crista Galli (CG); Left Sphenoidal Sinus (LSS); Right Sphenoidal Sinus (RSS); Posterior Ethmoidal Cell (PEC); Ethmoidal Cells (ECs)
2011, 1 case (50/m) symmetric hypothalamic lesions extending to optic tracts and chiasma. CT chest -pericardial, pleural effusion.
(46) A chiasma takes the form A-B-B'-A, where the initial
During diplotene, diakinesis and metaphase I, 16 autosomal bivalents and three univalent sex chromosomes were seen; generally, one chiasma (i.e., interstitial or terminal type) per bivalent was observed (Fig.
His pituitary MRI demonstrated a pituitary macroadenoma with cavernous sinus invasion and suprasellar extension, impinging and displacing the optic chiasma. He had normal visual fields, normal height (178.2 cm, midparental height: 174.5 cm), and no symptoms of acromegaly.
Male diplotene/metaphase I nuclei showed four autosomal bivalents, with one terminal or interstitial chiasma in M.