chiasma

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.

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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.

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chi·asmal, chi·asmic, chias·matic (-mtk) adj.

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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.

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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.