chiasma
Americannoun
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Anatomy. a crossing or decussation, as that of the optic nerves at the base of the brain.
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Cell Biology. a point of overlap of paired chromatids at which fusion and exchange of genetic material take place during prophase of meiosis.
noun
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cytology the cross-shaped connection produced by the crossing over of pairing chromosomes during meiosis
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anatomy the crossing over of two parts or structures, such as the fibres of the optic nerves in the brain
Other Word Forms
Derived Forms
Inflected Forms
Nouns
Etymology
Origin of chiasma
1830–40; < Greek: crosspiece of wood, cross-bandage, equivalent to chi chi 1 + -asma noun suffix
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
There must be at least one chiasma per chromosome for proper separation of homologous chromosomes during meiosis I, but there may be as many as 25.
From Textbooks ● Jun. 9, 2022
Pressure on the optic chiasma, for example by a tumour of the pituitary body, is associated with bilateral temporal hemianopsia.
From Manual of Surgery Volume Second: Extremities—Head—Neck. Sixth Edition. by Miles, Alexander
The movement follows the course of the optic nerve, traverses the chiasma, goes along the fascia, passes the internal capsule, and finally arrives at the visual centres of the occipital region.
From The Mind and the Brain Being the Authorised Translation of L'Âme et le Corps by Binet, Alfred
We know that they are directly connected by fibres that arch round through the chiasma.
From Medical Essays, 1842-1882 by Holmes, Oliver Wendell
They have an arterial cone and bulb, spiral intestinal valve, and the optic nerves united by a chiasma.
From The Gutenberg Webster's Unabridged Dictionary Section F, G and H by Project Gutenberg
The chiasmata remain until anaphase I. The number of chiasmata varies according to the species and the length of the chromosome.
From Textbooks ● Jun. 9, 2022
Scientists thought chiasmata were a variation on synapsis and could not understand how chromosomes could break and rejoin.
From Textbooks ● Jun. 9, 2022
The homologous chromosomes are still held together at chiasmata.
From Textbooks ● Jun. 9, 2022
As prophase I progresses, the close association between homologous chromosomes begins to break down, and the chromosomes continue to condense, although the homologous chromosomes remain attached to each other at chiasmata.
From Textbooks ● Apr. 25, 2013
The number of chiasmata varies with the species and the length of the chromosome.
From Textbooks ● Apr. 25, 2013
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
