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 ?
Hilary's experience which was un-pressured, un-hurried, gentle, and thoughtful, gives heed to the chiasm Merleau-Ponty spoke of.
Surgery may be considered for patients who have pituitary incidentalomas if there is clinically significant growth of the lesion, loss of endocrino-logic function, or an "unremitting headache," or if a patient is planning a pregnancy and has a lesion close to the optic chiasm.
Pituitary adenomas usually grow by expansion locally within the sella and upward toward the optic chiasm.
Discussing one of the earliest forms of thought, the chiasm, Rodolphe Gasche, for example, explains, "it allows the drawing apart and bringing together of opposite functions or terms and entwines them within an identity of movements" (Gasche 273).
Since the dialogue is conditioned by the anonymous intentionality of the "prepersonal tradition", the phenomenology of the lived body is in Merleau-Ponty's work a prelude to an ontology of the human-nature chiasm (20).
To this end, hypophysis and hypothalamus at the optic chiasm zone were quickly removed and cut into 1cm-thick coronal sections.
Severe cranial trauma can "split" the optic chiasm and produce a bitemporal hemianopia.
The Institute of Medicine's 2001 report Crossing the Quality Chiasm states that the U.
The etiologies of their visual impairments included retinopathy of prematurity, glaucoma, retinal detachment, amaurosis, optic chiasm tumors, sarcoid growth, injury, retinitis pigmentosa, diabetic retinopathy, retinal blastoma, macular degeneration, and unknown.
The work being done by the group has already helped young patients like five-year-old Poppy Guilder, who has been treated for a rare type of brain tumour - an optic chiasm glioma - at Birmingham Children's Hospital since she was 14 months-old.
Maura's intermittent diplopia, ptosis, ataxia, and anorexia with weight loss are typical findings with lesions in the deep brain structures near the optic chiasm, thalamus, and third cranial nerve.
Cranial MRI showed obvious focal contrast enhancement in cerebral and cerebellar tissues, tension of the infundibular stalk and inferior shift at the optic chiasm.