chromatin


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chromatin:

see chromosomechromosome
, structural carrier of hereditary characteristics, found in the nucleus of every cell and so named for its readiness to absorb dyes. The term chromosome
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.

Chromatin

 

chromosome substance found in the nuclei of plant and animal cells. Chromatin stains intensively with nuclear stains and, at the time of cell division, forms certain visible structures in the chromosomes. The term was introduced in 1880 by the German histologist W. Flemming. Present-day cytologists generally understand chromatin to be chromosomal material of the cell nucleus in interphase (between its successive divisions), since chromosomes in that period of cell cycle are not easily detected under the microscope. Chromatin is made up of deoxyribonucleic acid (DNA, 30–40 percent), ribonucleic acid (RNA), histones, and nonhistone proteins. The main structural components of chromatin are deoxyribonucleoprotein strands measuring 100–200Å in diameter and based on, according to most investigators, one molecule of DNA.

American scientists have proposed two models of the fine structure of a primary chromatin strand: super-coil (J. F. Pardon and M. H. F. Wilkins, 1972) and spheroid (R. D. Kornberg, 1974; A. L. Olins and D. E. Olins, 1974). The spheroid model, which has been better substantiated experimentally, supposes that the primary chromatin strand is a flexible chain of repeating subunits—that is, nucleosoma—which is a bent DNA section of 150–200 pairs of nucleotides and a complex of eight histone molecules.

Genetically active chromatin (euchromatin) is differentiated from inactive chromatin (heterochromatin). The cell nuclei of females of many organisms—especially mammals (including man)—contain dense masses of chromatin called sex chromatin. Such masses, which are not present in males, apparently are formed in females by inactive sections of the sex chromosomes, mainly from the heterochromatin of one of the paired X chromosomes.

I. I. KIKNADZE

chromatin

[′krō·mə·tən]
(biochemistry)
The deoxyribonucleoprotein complex forming the major portion of the nuclear material and of the chromosomes.

chromatin

Cytology the part of the nucleus that consists of DNA and proteins, forms the chromosomes, and stains with basic dyes
References in periodicals archive ?
A specialized class of proteins, known as pioneer transcription factors (PTFs), is responsible for opening up the chromatin at particular sites.
In the nucleus of cells, DNA wraps itself around histone proteins forming a 'beads-on-a-string' structure called chromatin. Other proteins bind along chromatin and the structure folds further into more complicated configurations.
The more insights researchers can gain about chromatin, the more likely they can one day be able to regulate gene expression, which could change how people are treated for diseases like cancer and Alzheimer's.
These methods are based on the ability of some stains to assess the conformation of sperm chromatin, which in turn depends on DNA interaction with proteins (18, 19).
In addition to high-quality genome assemblies, other labs demonstrated the ability to detect chromatin loops and topologically associated domains with high confidence at significantly reduced depth of sequencing compared to other methods.
To overcome the problem of visualizing chromatin in an intact nucleus, O'Shea's team screened a number of candidate dyes, eventually finding one that could be manipulated precisely with light to undergo a complex series of chemical reactions that essentially would "paint" the surface of DNA with a metal so that its local structure and 3D polymer organization could be imaged in a living cell.
Chromatin immunoprecipitation (ChIP) assays with sequencing or ChIP-Seq is a sequencing technology generally utilized to study genome-wide H3 trimethylation--H3K4me3 and H3K27me3.
As Ep400/Tip60 is involved in chromatin compaction, this observation identifies an interesting link between chromatin 'openness' with increased potency.
Recently, toluidine blue, a nuclear stain used to evaluate chromatin integrity [4, 26, 31] has been used successfully to morphometric analysis by CASMA [4, 34, 38], and this combination has opened the possibility to evaluate simultaneously the sperm head morphometry and chromatin integrity as well as their relationship and could be a powerful tool to improve the results of spermiogram [33].
Histone PTMs also play important roles in histone nuclear import and chromatin assembly (Burgess and Zhang 2013; Ejlassi-Lassallette et al.
pRB-Mediated Repression of Gene Transcription via Chromatin Structure Modification