| 释义 |
recombiˈnation
[re- 5 a.]
1. The action or an instance of recombining.
1828in Webster. 1847A. de Morgan Formal Logic xi. 218 It is good against those who confound analysis and recombination of existing materials with introduction of them. 1850Grote Greece ii. lxvii. (1862) VI. 45 Was it a decomposition and recombination of elements still continuing? 1873Symonds Grk. Poets xi. 344 A complete revision and recombination of all pre-existing anthologies.
2. Physics. The recombining of ions and electrons to form neutral atoms. Freq. attrib.
1897Phil. Mag. XLIV. 424 When a gas is acted on by the Röntgen rays a steady state is reached when the rate of production of the ions by the rays is equal to their rate of recombination. 1942J. D. Stranathan ‘Particles’ Mod. Physics i. 8 Let us suppose that there are n pairs of ions present per cc. at any time, n positive ions and n negative ions... The number of recombinations R per cc. per second is then given by R = αn2 where α is a constant called the coefficient of recombination. 1962Guardian 10 July 9/5 Atoms in the atmosphere would be broken up in extremely large numbers, so that this recombination light would be visible even to the naked human eye. 1969J. J. Sparkes Transistor Switching i. 13 It will first have to supply the recombination current for any charge already present. 1974Encycl. Brit. Macropædia XIV. 506/2 Other forms of radiation met with in plasma physics include line and recombination radiation.
3. Genetics.
a. The formation by a sexual process of genotypes that differ from both the parental genotypes.
1903Proc. Cambr. Philos. Soc. XII. 53 Since the resolution of a compound character may be spoken of as an analysis leading to a distribution of the components among the gametes, the term synthesis should surely be reserved for a recombination that has taken place in such a way that the gametes become bearers of the compound character again, as they were in the pure compound form. 1909W. Bateson Mendel's Princ. Heredity iii. 71 These cases of novelties resulting through a re-combination of the factors brought in by the original pure types are striking because it is not at first sight evident how the novelty has been produced. 1941J. S. Huxley Uniqueness of Man iv. 107 Recombination—i.e...reshuffling of old genes in new constellations owing to independent assortment after a cross. This accounts for most of the differences observed between brothers and sisters in the same family. 1976Times Lit. Suppl. 6 Aug. 985/2 Recombination was an idea that Darwin had lacked in his attempt to explain how natural selection and breeding were connected.
b. The formation by crossing-over of chromosomes that differ from both the chromosomes from which they derive. Also attrib.
1923Bridges & Morgan Third-Chromosome Group of Mutant Characters of Drosophila Melanogaster i. 9 If Dichæte is crossed to pink, and the F1 female is back-crossed to a pink male, most of the flies are of the two original types, Dichæte or pink; but a small number of the offspring are both Dichæte and pink or neither (i.e., wild-type). These two latter classes are called ‘recombination classes’ and the ‘percentage of recombination’ may be found... The use of the term ‘recombination’ in this technical sense is a shortening of the full term ‘recombination of linked characters’. 1939C. D. Darlington Evolution of Genetic Systems xiv. 77 This recombination we now see is more profound than Weismann imagined. It extends beyond the chromosomes to the genes. The number of units capable of recombination is not five or even fifty, but five thousand or fifty thousand. Ibid., Taking the sum of the haploid number of chromosomes and of the average chiasma frequency of all the chromosomes in a meiotic cell as a recombination index. 1940Jrnl. Genetics XL. 429 Let x be the recombination frequency. 1943Biol. Rev. XVIII. 50 In one set of individuals AB and ab may be more favoured than Ab and aB, the reverse may be true elsewhere and, as recombination is the only means short of mutation of changing the arrangement, this inconstancy of advantage must favour some degree of recombination. 1955Jrnl. Gen. Microbiol. XIII. 346 Genetic recombination has now been demonstrated amongst several viruses. 1965Proc. Nat. Acad. Sci. LIII. 457 The term ‘recombination’ when used in the context of bacterial genetics connotes to many either the process of DNA transmission known as conjugation or the formation by conjugation of any progeny which inherit phenotypic traits derived from both parents. It can, however, be used more strictly to denote the series of physical and chemical events which serve to link genes derived from one parental DNA with those derived from another parental DNA. 1976National Observer (U.S.) 5 July 6/1 The object of these guidelines is to ensure that experimental DNA recombination will have no ill effects on those engaged in the work, on the general public, or on the environment. 1977A. W. F. Edwards Foundations Math. Genetics viii. 94 Linkage is not complete, and its magnitude is measured by the recombination fraction, r, between the two loci. |