chiasman.

Brit.

/kʌɪˈazmə/, U.S.

/kaɪˈæzmə/

Forms: Also chiasm.

Etymology: modern Latin, < Greek χίασμα arrangement of two lines (sticks, etc.) crossed like the letter Χ (χῖ), decussation; χιάζειν to mark with or like a chī (Χ, χ).

Anatomy.

1. Intercrossing or decussation. optic chiasma n. the crossing or decussation of the fibres of the optic nerves at the base of the brain; the optic commissure.

ΘΚΠ

the world > life > the body > bodily substance > fibre > [noun] > network of

texture1578

plexus1666

plexure1672

weaving1739

chiasma1839

incruciation1855

1839–47 Todd's Cycl. Anat. & Physiol. III. 769/1 The existence of a chiasma is not general throughout the animal series.

1873 St. G. Mivart Lessons Elem. Anat. ix. 387 This decussation of fibres is called the optic commissure or chiasma.

1880 A. Günther Introd. Study of Fishes 104 In Palæichthyes the two nerves are fused together, immediately after their origin, into a chiasma.

2. Cytology. Plural chiasmata. [French (F. A. Janssens Cellule (1909) xxv. 391).] The exchange of segments of chromatids during nuclear division.

ΘΚΠ

the world > life > biology > biological processes > genetic activity > [noun] > changes or actions of genes or chromosomes > cross-over

recombination1903

chiasma1911

crossing-over1912

crossover1912

interference1916

1911 T. H. Morgan in Science XXXIV. 637/1 The chiasma type of cross union between the homologous chromosomes is grasped.

1911 T. H. Morgan in Science XXXIV. 637/1 If, then, the genes do not themselves split when the chiasma is formed there is no opportunity offered for a quantitative division.

1929 C. D. Darlington in Nature 20 July 99/2 In the longer chromosomes these chromatids change partners, forming what are called ‘chiasmata’... In the short chromosomes..there is rarely more than one chiasma.

1949 New Biol. 7 83 Each chiasma represents a point where two of the four daughter chromatids, one from each of the pairing partners, have broken and rejoined with one another, thus giving rise to two new continuous strands which cross over from one partner to the other.

This entry has not yet been fully updated (first published 1889; most recently modified version published online June 2022).

单词	chiasma
释义	chiasman. Brit. /kʌɪˈazmə/, U.S. /kaɪˈæzmə/ Forms: Also chiasm. Etymology: modern Latin, < Greek χίασμα arrangement of two lines (sticks, etc.) crossed like the letter Χ (χῖ), decussation; χιάζειν to mark with or like a chī (Χ, χ). Anatomy. 1. Intercrossing or decussation. optic chiasma n. the crossing or decussation of the fibres of the optic nerves at the base of the brain; the optic commissure. ΘΚΠ the world > life > the body > bodily substance > fibre > [noun] > network of texture1578 plexus1666 plexure1672 weaving1739 chiasma1839 incruciation1855 1839–47 Todd's Cycl. Anat. & Physiol. III. 769/1 The existence of a chiasma is not general throughout the animal series. 1873 St. G. Mivart Lessons Elem. Anat. ix. 387 This decussation of fibres is called the optic commissure or chiasma. 1880 A. Günther Introd. Study of Fishes 104 In Palæichthyes the two nerves are fused together, immediately after their origin, into a chiasma. 2. Cytology. Plural chiasmata. [French (F. A. Janssens Cellule (1909) xxv. 391).] The exchange of segments of chromatids during nuclear division. ΘΚΠ the world > life > biology > biological processes > genetic activity > [noun] > changes or actions of genes or chromosomes > cross-over recombination1903 chiasma1911 crossing-over1912 crossover1912 interference1916 1911 T. H. Morgan in Science XXXIV. 637/1 The chiasma type of cross union between the homologous chromosomes is grasped. 1911 T. H. Morgan in Science XXXIV. 637/1 If, then, the genes do not themselves split when the chiasma is formed there is no opportunity offered for a quantitative division. 1929 C. D. Darlington in Nature 20 July 99/2 In the longer chromosomes these chromatids change partners, forming what are called ‘chiasmata’... In the short chromosomes..there is rarely more than one chiasma. 1949 New Biol. 7 83 Each chiasma represents a point where two of the four daughter chromatids, one from each of the pairing partners, have broken and rejoined with one another, thus giving rise to two new continuous strands which cross over from one partner to the other. This entry has not yet been fully updated (first published 1889; most recently modified version published online June 2022). < n.1839
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