Heterochromatin

heterochromatin
highly condensed chromatin that stains deeply; thought to be genetically inert
Source: Jenkins, John B. 1990. Human Genetics, 2nd Edition. New York: Harper & Row ...
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Heterochromatin is believed to serve several functions, from gene regulation to the protection of the integrity of chromosomes; all of these roles can be attributed to the dense packing of DNA, ...
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Heterochromatin that surrounds the centromere. Specific regions of heterochromatin always present and in both homologs of a chromosome. See satellite DNA.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z ...
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The heterochromatin common to all active cells is designated constituitive heterochromatin. It does not contain "genes". Heterochromatin is not being transcribed and consists, in part, of satellite DNA.
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Heterochromatin properties are mediated by proteins specifically associated with satDNAs that, however, are poorly characterized.
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Heterochromatin
The term proposed by Heitz (1928) for parts of chromosomes with an abnormal degree of contraction or of staining properties at nuclear divisions (Gk. heteros, different). Composed of repetitive DNA, stains dark bands in G-banding. (Cf.
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Heterochromatin stains more strongly and is a more condensed chromatin. Euchromatin stains weakly and is more open (less condensed). Euchromatin remains dispersed (uncondensed) during Interphase, when RNA transcription occurs.
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Heterochromatin and Euchromatin
Heterochromatin is tightly wound DNA and visible during interphase. It is inactive because DNA cannot be transcribed while it is tightly wound.
Euchromatin is not tightly wound. It is active.
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Heterochromatin
is found in parts of the chromosome where there are few or no genes, such as
centromeres and
telomeres ...
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heterochromatin Chromatin that stains intensely and appears to represent inactive genetic areas.
heterochrony Evolutionary change in the relative time of appearance or rate of development of characteristics from ancestor to descendant.
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Heterochromatin. Dark-stained regions of chromosomes thought to be for the most part genetically inactive.
Heteroduplex. A double-stranded DNA molecule or DNA-RNA hybrid, where each strand is of a different origin.
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Heterochromatin: Compact, gene-poor regions of a genome, which are enriched in simple sequence repeats. As it can be impossible to clone, heterochromatin is often ignored when calculating the percentage of a genome that has been sequenced.
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Heterochromatin
Chromatin is the extended form of DNA-protein complex present in the nucleus during interphase in eukaryotic cells. It can be made visible by staining (thus the name which literaly means coloured material).
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Heterochromatin. Dark-stained regions of chromosomes thought to be for the most part genetically inactive. Heteroduplex. A double-stranded DNA molecule or DNA-RNA hybrid, where each strand is of a different origin. Heterogeneous nuclear RNA (hnRNA).
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hept- seven hetero- different heterochromatin Chromatin which in a condensed, less accessible state and are thus frequently transcriptionally silent. However, some DNA is constitutive heterochromatin (e.g.
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It exists in two forms: less dense euchromatin can be transcribed, and heterochromatin is highly condensed and cannot be transcribed. Inactive X chromosome of female mammals is an example of heterochromatin. See
Gene Expression
.
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