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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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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.



The deoxyribonucleoprotein complex forming the major portion of the nuclear material and of the chromosomes.


Cytology the part of the nucleus that consists of DNA and proteins, forms the chromosomes, and stains with basic dyes
References in periodicals archive ?
As mentioned earlier, DNA methylation can inhibit transcription indirectly, via MBDs that seem to regulate the condensation of chromatin structure and recruit HDACs and DNMTs.
Likewise, Weaver and colleagues (2004) demonstrated that maternal behavior was able to produce stable alterations in DNA methylation and chromatin structure in the hippocampus of their offspring that persisted into adulthood.
Key words Assisted reproduction techniques--DNA fragmentation--DNA integrity--oxidative stress--sperm chromatin structure assay
III] at concentrations up to 50 [micro]M also failed to relax the chromatin structure (Figure 7).
Therefore, the attention has now shifted from analysing standard semen parameters to studying/ evaluating molecular aspects of spermatozoa, among these are sperm chromatin structure assay, free radical levels, sperm transcript and telomere length (6, 7, 9).
Together, these three proteins hold an integral role in coding histones with covalent tail modifications, thereby affecting chromatin structure and the subsequent regulation of gene expression.
Manipulating Higher Order Chromatin Structure of the [eth]-Globin Locus by Targeted Tethering of a "Looping" Factor
Specific topics include mechanistic studies of the mRNA transcription cycle, the relationship between higher-order chromatin structure and transcription, specialized transcription factories, a role for upstream binding factor in organizing ribosomal gene chromatin, nutrient-regulated gene expression in eukaryotes, nucleosome dynamics, non- coding RNA in transcription initiation, fluorescence resonance energy transfer as a method for dissecting in vivo mechanism of transcriptional activation, and core promoter-selective RNA polymerase II transcription.
This modification alters chromatin structure to influence gene expression.
The destabilization of such regulatory mechanisms that act on the chromatin structure are implicated in pathologies such as cancer.
1-2 Covalent modifications, such as acetylation, methylation and phosphorylation affect chromatin structure and exquisitely regulate gene expression.
The IP-Star launch comes at an important time for the field, given increased interest and exciting new research identifying broad, important roles for epigenetics (including changes in chromatin structure, histone modifications, DNA binding proteins, and DNA methylation) in cancer, genome-wide RNA regulation, development, differentiation, stem cells, diabetes, and other human diseases.