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chiasma

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chiasma /chi·as·ma/ (ki-az´mah) pl. chias´mata   [L.] chiasm; in genetics, the points at which members of a chromosome pair are in contact during the prophase of meiosis and because of which recombination, or crossing over, occurs on separation.
chi·as·ma (k-zm) or chi·asm (kzm)
n. pl. chi·as·mas or chi·as·ma·ta (-m-t) or 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·asmal, chi·asmic, chias·matic (-mtk) adj.

chiasma
[kī·az′mə] pl. chiasmata
Etymology: Gk, lines that cross
a visible connection between homologous chromosomes during the first meiotic division in gametogenesis. Chiasmata appear as X-shaped configurations during the late prophase stage and provide the means by which homologous chromosomes exchange genetic material. See also crossing over. chiasmatic, chiasmic, adj.

chiasma [ki-az´mah] (pl. chias´mata) (L.; Gr.)
in genetics, the points at which members of a chromosome pair are in contact during the prophase of meiosis and because of which recombination, or crossing over, occurs on separation. See also chiasma formation.

chiasma
pl. chiasmata [L., Gr.] chiasm; in genetics, the points at which members of a chromosome pair are in contact during the prophase of meiosis and because of which recombination, or crossing over, occurs on separation.

chiasma formation
the process by which a chiasma is formed; it is the cytological basis of genetic recombination, or crossing over.
chiasma syndrome
optic atrophy with bilateral hemianopia.


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To more closely examine brain tissue for neuronal damage, three cross sections of brain (level of optic chiasma, caudal to mammillary bodies and caudal to transverse fibers of the pons) were stained with luxol fast blue-cresyl violet.
When they do occur, mucoceles isolated to the sphenoid sinus cause symptoms related to surrounding structures that are vulnerable to compression, including the pituitary gland, optic nerve, chiasma, and the structures found within the cavernous sinus.
Each heterochromatic block, through its chiasma displacement effect, can keep in its proximity certain favorable allele combinations of different genes ("coadapted gene pools") (17).
 
 
 
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