Heterochromatin


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heterochromatin

[¦hed·ə·rō′krō·məd·ən]
(cell and molecular biology)
Specialized chromosome material which remains tightly coiled even in the nondividing nucleus and stains darkly in interphase.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Heterochromatin

 

portions of the chromosomes that remain thickened in the interval between cell divisions, that is, in the interphase (as opposed to other portions called euchromatin). Heterochromatin is sometimes closely associated with the nucleolus, forming a sort of ring or casing around it. During mitosis the heterochromatin is colored more or less darkly than the euchromatin (the phenomenon of positive or negative heteropycnosis). Heterochromatin is especially characteristic of sex chromosomes of many animal species. Heteropycnotic areas can be obtained experimentally, for example, through the action of low temperature. It is theorized that heterochromatin does not contain genes that control the development of the organism.

M. E. ASPIZ

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Tapscott, "Antisense transcription and heterochromatin at the DM1 CTG repeats are constrained by CTCF," Molecular Cell, vol.
Some senescent cell types are characterized by nuclear heterochromatin foci that can be visualized by DNA-stains and the increased expression of heterochromatin protein 1 gamma (HP1[gamma]) [28, 29].
Trimethylated H3K9 (H3K9me3) is a highly conserved histone post-translational modification and is commonly linked to both facultative and constitutive heterochromatin formation and transcriptional repression.
The distribution of constitutive heterochromatin (C-banding) in this specimen showed pericentromeric bands in all autosomes.
Perieentric heterochromatin becomes enriched with H2aZ during early mammalian development.
TERMINAL FLOWER 2/LIKE HETEROCHROMATIN PROTEIN 1 (TFL2/LHP1), the Arabidopsis homologue of animal HP1, binds to histone H3K9me2 or H3K9me3 and to H3K27me3.
Epigenetic codes for heterochromatin formation and silencing: rounding up the usual suspects.
(3) Heterochromatin is a tightly packed complex of DNA and proteins in the cell nucleus in which the DNA is not easily accessible to other proteins and therefore generally is not expressed.
It contained mainly euchromatin and only small granules of heterochromatin. The second nucleus, seen at the sharpest distinction, was small, often spindle-shaped, and dark.
Detection of constitutive heterochromatin (C-banding) was performed according to Sumner (1972), with some minor modifications.