chiasma


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chiasma

(kīăz`mə): see crossing overcrossing over,
process in genetics by which the two chromosomes of a homologous pair exchange equal segments with each other. Crossing over occurs in the first division of meiosis. At that stage each chromosome has replicated into two strands called sister chromatids.
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chiasma

[kī′az·mə]
(anatomy)
A cross-shaped point of intersection of two parts, especially of the optic nerves.
(cell and molecular biology)
The point of junction and fusion between paired chromatids or chromosomes, first seen during diplotene of meiosis.
References in periodicals archive ?
napus revealed that out of 855 bivalents, in 45 sampled PMC's, the number of rod bivalents, ring bivalents, number of chiasma and chiasma per cell were 349, 506, 1362 and 30.26, respectively.
Kleckner, "Chiasma formation: Chromatin/axis interplay and the role(s) of the synaptonemal complex," Chromosoma, vol.
For the "anamorphic effect" is in the nature of a mnemonic tribute to the abstract decorative patterns in Islamic architecture--the counterpoint to Minimalism in her aesthetic imaginary--and the geometric basis of the optical haze of coloured light is her appropriately abstract and secular transposition of the chiasma of the numinous and the luminous that is the exemplary Islamic form of encomium to the sacred (figures 9a and 9b).
Cranial and pituitary magnetic resonance (MR) imaging revealed a mass with a size of approximately 3x3,5x3 cm which filled the base of the sella, obstructed the suprasellar cistern, formed crenation in the base of the third ventricle, compressed the left optic nevre and the optic chiasma on the left with regular borders having the same intensity as the heterogeneous gray matter in the T1A and T2A sequences and contrast enhancement following intravenous injection of contrast material (Figure 2).
The pituitary gland grows physiologically during pregnancy; this can lead to changes such as bitemporal concentric visual field defects in cases of an abnormal anatomical relationship between the pituitary gland and the optic chiasma. (18)
Biopharmaceutical company Chiasma (NasdaqGS:CHMA) disclosed on Monday that it recorded a net loss of USD8.0m (USD50.36 net loss per basic common share) for the second quarter ended 30 June 2015.
Chiasma's shares began trading on the NASDAQ Global Select Market on Thursday, July 16, 2015 under the ticker symbol CHMA.
The hypothalamus is located at the base of the forebrain beneath the thalamus and posterior to the optic chiasma. It coordinates the endocrine system and acts as a bridge between this and the nervous system.
From a total of 20 analyzed trivalents, all had only one chiasma per chromosome arm and 70% of them were distal, 35% interstitial and 5% proximal.
Two-point crossover is used to the chromosomal chiasma in this paper; firstly produce a random real number Sc which in [0, 1], if Sc is less than the crossover probability Pc, then select individuals [a.sub.i] and [a.sub.j] randomly to crossover.