| 释义 |
non-disˈjunction
[non- 1.]
1. Cytology. The failure of one or more pairs of homologous chromosomes (at meiosis) or sister chromatids (at mitosis) to separate and move away normally from the equatorial plate during nuclear division, usu. with the result that one of the daughter nuclei has too few chromosomes and the other too many.
1913Jrnl. Exper. Zoöl. XV. 587 (heading) Non-disjunction of the sex chromosomes of Drosophila. 1925Jrnl. Genetics XV. 251 Non-disjunction was long ago observed in the diploid Oenothera. 1961Lancet 5 Aug. 319/2 The mosaicism reported here could have originated in several ways. Mitotic nondisjunction in a normal diploid embryo could result in 1 cell with forty-eight chromosomes (trisomy for chromosome 21 and chromosome 19 or 20) and 1 non-viable cell with forty-four chromosomes. 1962Ibid. 15 Dec. 1270/1 Three types of meiotic non-disjunction have been recognised. 1971Levitan & Montagu Testbk. Human Genetics iii. 63 Changes in the total number of chromosomes most frequently result from the occasional failure of chromosomes to move to opposite poles or disjoin during anaphase of cell division. Such a failure is called non-disjunction.
2. Logic. The relation of the terms in a proposition asserting the negative of a disjunctive proposition (‘neither..nor..’).
1956,1965[see non-conjunction 2].
Hence non-disˈjunctional a. Cytology.
1913Jrnl. Exper. Zoöl. XV. 589, 10 per cent of the eggs of such a female matured in a non-disjunctional manner. Ibid. 590, I counted the offspring of the non-disjunctional male only with respect to white and pink. 1930Genetics XV. 11 These seven non-disjunctional males were red. 1971Levitan & Montagu Textbk. Human Genetics iii. 66 Nondisjunctional error in meiosis could involve all 23 pairs of chromosomes. |