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.

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

References in periodicals archive ?
Studying mutations to the ATF-2 gene in Drosophila (dATF-2), the researchers observed a disruption to the heterochromatin structure and reduced methylation of histone proteins, the main component of chromatin.
Heterochromatin heterogeneity and chromosome heteromorphism in Cerdocyon thous (Mammalia: Canidae).
The nucleus has an oval to irregular shape and contains a nucleolus and numerous heterochromatin particles.
Nuclear body components can contact chromatin by interacting with a heterochromatin protein, thereby providing a link between nuclear bodies and the chromatin.
The nearly hemispherical retina is composed of a layer of epithelial retinular cells containing basally (or peripherally) located nuclei with a distinctive arrangement of heterochromatin (Fig.
rubrioculus exhibit a 2n=48 karyotype with exclusively acrocentric (NF=48) chromosomes, one pair of NORs interstitially located on chromosome pair number 8 and constitutive heterochromatin distributed in pericentromeric position of all chromosomes.
Most of the neurons showed reduced cytoplasm and large, elongated nuclei with peripheral and central accumulations of dense heterochromatin (Fig.
The type I intimal cell was characterized by abundant vacuoles and lysosomes, big and dense mitochondria, a nucleus mainly consisting of heterochromatin and a poorly developed rough endoplasmic reticulum.
Giemsa C-banding technique, which stains constitutive heterochromatin, is a technique that has been used successfully in many species to identify individual chromosomes and to establish genomic relationships among species (Fominaya et al.
Localization of the heterochromatin in human chromosomes.
These heterochromatin differences are the likely cause of a striking DNA content variation (approximately 30%) between Andean and non-Andean insects.