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.

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 It might be outdated or ideologically biased.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

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References in periodicals archive

Tapscott, "Antisense transcription and heterochromatin at the DM1 CTG repeats are constrained by CTCF," Molecular Cell, vol.

Transcriptionally repressive chromatin remodelling and CpG methylation in the presence of expanded CTG-repeats at the DM1 locus

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].

Cell senescence in myxoid/round cell liposarcoma

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.

ChIP-seq analysis of histone H3K9 trimethylation in peripheral blood mononuclear cells of membranous nephropathy patients

The distribution of constitutive heterochromatin (C-banding) in this specimen showed pericentromeric bands in all autosomes.

Diferenciacao cromossomica em Kerodon rupestris (Rodentia: Caviidae) da regiao semiarida brasileira

Perieentric heterochromatin becomes enriched with H2aZ during early mammalian development.

The role of epigenetics in spermatogenesis Epigenetigin spermatogenezdeki rolu

TERMINAL FLOWER 2/LIKE HETEROCHROMATIN PROTEIN 1 (TFL2/LHP1), the Arabidopsis homologue of animal HP1, binds to histone H3K9me2 or H3K9me3 and to H3K27me3.

Histones and plant hormones: new evidence for an interesting interplay

X chromosome inactivation: heterogeneity of heterochromatin. Biochem Cell Biol 2008; 86: 370-379

X chromosome inactivation in mammalian embryonic development/Inactivacion del cromosoma x en el desarrollo embrionario mamifero/Inativacao do cromossomo x no desenvolvimento embrionario dos mamiferos

Epigenetic codes for heterochromatin formation and silencing: rounding up the usual suspects.

Expression enhancement in trastuzumab therapeutic monoclonal antibody production using genomic amplification with methotrexate

(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.

Dysregulation of microRNA expression and function contributes to the etiology of fetal alcohol spectrum disorders

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.

Increased cell fusion in cerebral cortex may contribute to poststroke regeneration

Detection of constitutive heterochromatin (C-banding) was performed according to Sumner (1972), with some minor modifications.

Description of the karyotype of Geophagus cf. proximus (Perciformes, Cichlidae, Geophaginae)/Descricao do cariotipo de Geophagus cf. proximus (Perciformes, Cichlidae, Geophaginae)