Akademik

chiasma
SYN: chiasm. [G. c., two crossing lines, fr. the letter chi, 3]
- c. opticum [TA] SYN: optic chiasm.
- c. tendinum [TA] SYN: tendinous chiasm of the digital tendons.

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chi·as·ma kī-'az-mə, kē- n, pl -ma·ta -mət-ə
1) an anatomical intersection or decussation see OPTIC CHIASMA
2) a cross-shaped configuration of paired chromatids visible in the diplotene of meiotic prophase and considered the cytological equivalent of genetic crossing-over
chi·as·mat·ic .kī-əz-'mat-ik, .kē- adj

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n. (pl. chiasmata)
1. (in genetics) the point at which homologous chromosomes remain in contact after they have started to separate in the first division of meiosis. Chiasmata occur from the end of prophase to anaphase and represent the point at which mutual exchange of genetic material takes place (see crossing over).
2. see optic chiasma.

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chi·as·ma (ki-azґmə) pl. chiasґmata [L., from Gr. “a cross, crosspiece,” from the shape of the letter chi (X)] 1. an anatomical term for a decussation or X-shaped crossing, such as of nerves. 2. a point where pairs of homologous chromatids remain in contact during late prophase to anaphase of meiosis I, indicating where an exchange of homologous segments has taken place between nonsister chromatids by recombination.

Medical dictionary. 2011.