| 释义 |
bivalent, a. and n.|ˈbɪvələnt|
[f. bi- prefix2 III + -valent, ad. L. valēntem, pr. pple. of valēre to be worth.]
1. Chem. Combining with two atoms of an element or radicle; also divalent.
1869Eng. Mechanic 12 Nov. 198/3 The elements are classified as..diatomic or bivalent..as sulphur. 1880E. Cleminshaw Wurtz' Atom. The. 121 Mercury, cadmium, and probably other bivalent metals.
2. Biol. Applied to homologous chromosomes united in pairs at the first division of meiosis. Hence as n.
1899J. H. McGregor in Jrnl. Morphology XV. (Suppl.) 81 The only possibility of a true reduction..is by conceiving the chromosomes to be ‘bivalent’..and to assume that the halves of these bivalent chromosomes form new connections before the final mitosis. 1937Nature 30 Oct. 760/2 When the bivalent..attempts to divide, the ‘dicentric’ chromatid forms a bridge between the daughter nuclei. 1949Darlington & Mather Elements of Genetics i. 30 The compact paired, or bivalent, chromosomes..lie evenly in the nucleus. 1952New Biol. XIII. 35 Sometimes during the nuclear divisions, four chromosomes similar to each other all ‘pair’ together, forming a quadrivalent, instead of the usual two pairs of bivalents. |