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
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Because sperm head is composed by chromatin (DNA condensed by protamine proteins), the chromatin integrity, the shape sperm head and the sperm head morphometry should be related, and several studies have been published.
These acetylation modifications are critical for histone nuclear import and chromatin assembly.
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In a paper published on 3rd June in Science, researchers at the Centre for Genomic Regulation (CRG) led by senior group leader Miguel Beato in collaboration with the University Pompeu Fabra, the Institute for Biomedical Research in Barcelona, and the University Rovira i Virgili in Tarragona, Spain, have described for the first time a new pathway generating energy within the cell nucleus for remodelling chromatin and reprogramming gene expression.
Barr body: in 1949 Barr and Bertram noticed a jextanuclear chromatin in the nuclei of all female cells.
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However, due to the lack of suitable techniques and instruments, the chromatin organization inside a cell nucleus could not be observed in a non-invasive way with the sufficient resolution.
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The objective of this cross-sectional study was to assess the relationship of sperm parameters as well as chromatin integrity and apoptosis with IUI outcomes in two groups of patients with female or mild male factor infertility.
Although plant chromatin in general and histone proteins in particular as well as plant hormone signaling have been subjects of great interest during the last decade, the number of review articles concerning the effect of plant hormones on plant chromatin pattern are limited.
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Constellation will keep independent strategic direction, operational management and exclusive rights to programmes outside of the collaboration scope, including its two most advanced programmes that are focused on the development of inhibitors of the BET chromatin reader and EZH2 chromatin writer proteins.