| 释义 |
postreˈduction Genetics.
[a. G. postreduction (Korschelt & Heider Lehrb. der Vergleichenden Entwicklungsgeschichte der Wirbellosen Thiere (Allgemeiner Theil) (1903) II. vi. 595): see post- A. 1 b.]
a. Reduction of chromosome number at the second of the two meiotic cell divisions, rather than at the first. Opp. prereduction a.
1905Proc. Acad. Nat. Sci. Philadelphia LVII. 188 To the idea of postreduction we can apply the criticism ‘not proven’. 1915Jrnl. Morphol. XXVI. 122 In regard to the question of pre- and post-reduction, I have evidence here that the first maturation division is the reduction division. 1921L. W. Sharp Introd. Cytol. xi. 245 Such tetrads separate reductionally at the second mitosis (postreduction) rather than at the first (prereduction) in certain orthopterans.
b. Separation of homologous chromatids or genes at the second of the two meiotic cell divisions, rather than at the first. Opp. prereduction b.
1934L. W. Sharp Introd. Cytol. (ed. 3) xvi. 254 Disjunction in [meiosis] I is called ‘prereduction’; that in II, ‘postreduction’. 1950Adv. Genetics III. 221 The prereductional or postreductional division of the heterozygous allele pair depends on its situation in the bivalent. Let us consider only the most common bivalent type, a bivalent with prereduction in respect to centromere, and provided with one chiasma. (In contradistinction to this, the Lecanium species have postreduction.) 1967U. Mittwock Sex Chromosomes ix. 152 The sex chromosomes of Apodemus frequently exhibit postreduction, in contrast to most other mammals in which the X- and Y-chromosome show prereduction.
Hence postreˈductional a., involving or pertaining to postreduction; postreˈductionally adv.
1905Proc. Acad. Nat. Sci. Philadelphia LVII. 187 He is the solitary worker on the spermatogenesis of the Hemiptera who has taken the postreductional view. 1950[see postreduction b]. 1950Adv. Genetics III. 221 Since the number and situation of chiasmata, as a rule, varies even in the eggs of a single female, certain parts of a bivalent and consequently the gene pairs included in them may separate either prereductionally or postreductionally depending on the number and position of chiasmata. |