heteropycnosis Cytol.
(ˌhɛtərəʊpɪkˈnəʊsɪs)
Also -pyknosis.
[ad. G. heteropyknose (S. Gutherz 1907, in Arch. f. mikrosk. Anat. LXIX. 495), f. hetero- + Gr. πυκν-ός thick, dense: see -osis.]
The persistence of greater than average staining in chromosomal material; the character or condition, exhibited by some chromosomes or chromosomal regions in any particular nucleus, of being more (or, for negative heteropycnosis, less) condensed and hence appearing to take up more (or, less) stain than do the majority of chromosomes or chromosomal regions. Hence heteropycˈnotic a.
| 1925 E. B. Wilson Cell (ed. 3) x. 759 In the greater number of cases heteropycnosis first takes place after the final spermatogonial division. 1934 Genetics XIX. 467 In the latter species [sc. Drosophila melanogaster] he finds that about half of the X chromosome is heteropycnotic in the interphase. 1952 G. H. Bourne Cytol. & Cell Physiol. (ed. 2) v. 195 This property of heteropycnosis is especially characteristic of sex-chromosomes, such as the Y-chromosome of Drosophila species and the X-chromosomes of grasshoppers, but is also shown by many autosomal chromosome regions, and sometimes by whole autosomes. 1962 Lancet 19 May 1075/1 Once isopyknosis or heteropyknosis of a given X chromosome has been established, it is irreversible. 1963 Lewis & John Chromosome Marker i. i. 18 This positive heteropycnosis is later reversed and by metaphase-I the X has become negatively heteropycnotic and stains faintly. 1968 H. Harris Nucleus & Cytoplasm iv. 75 It is probable that other highly condensed heterochromatic or heteropyknotic regions in interphase nuclei also synthesize very much less RNA than the euchromatic regions. |