(redirected from Chromatin structure)
Also found in: Dictionary, Thesaurus, Medical.
Related to Chromatin structure: nucleosome


chromosome (krōˈməsōmˌ), structural carrier of hereditary characteristics, found in the nucleus of every cell and so named for its readiness to absorb dyes. The term chromosome is usually reserved for the structure when it is condensed and readily visible during cell division (see mitosis). At other times the chromosome appears as a fibrous structure, called the chromonema, consisting of accumulations (called chromomeres) of chromatin, the dye-absorbing material. During nuclear division, when each chromosome splits, each of the duplicate chromosomes is called a chromatid. A certain number of chromosomes is characteristic of each species of plant and animal; e.g., the human has 46 chromosomes, the potato has 48, and the fruit fly Drosophila has 8. Each of these chromosome numbers is the so-called diploid number, i.e., the number found in the somatic (body) cells and in the germ cells that give rise to the gametes, or reproductive cells. When the germ cells divide in the two-step process of meiosis, the chromosomes are separated in such a way that each daughter cell receives a haploid (half the diploid) number of chromosomes. Fusion of the male and female gametes in fertilization restores the diploid number in the fertilized egg, or zygote, which thus contains two sets of homologous chromosomes, one from each parent. The principal constituents of the chromosomes are nucleoproteins containing deoxyribonucleic acid, or DNA (see nucleic acid). Chromosomes appear microscopically as a linear arrangement of genes, the factors that determine the inherited characteristics of all living organisms. The very large chromosomes in the salivary gland cells of Drosophila and other insects have furnished valuable material for the study of genetics.
The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



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 Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The deoxyribonucleoprotein complex forming the major portion of the nuclear material and of the chromosomes.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


Cytology the part of the nucleus that consists of DNA and proteins, forms the chromosomes, and stains with basic dyes
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
In previous work Dang and colleagues had shown that in aging cells chromatin structure progressively falls apart.
HMGA2, present in both preadipocytes and preosteocytes, guarantees an open chromatin structure that initiates the two lineages through the factors introduced above.
The chromatin structure can be divided into two distinct categories based on the perspective of the association with gene transcription [32].
Several epigenetic mechanisms, including posttranslational histone modifications, DNA methylation, and microRNAs (miRNAs), determine the specific chromatin structure, consequently influencing gene transcription without altering the DNA sequence itself [61].
Histone acetylation opens the chromatin structure so that transcriptional activators can access the target promoter region and stimulate transcription.
Three of the advances that have significantly pushed the envelope on cell line development include the identification, optimization, and utilization of technologies that control chromatin structure to maximize expression of recombinant genes, the development of next generation sequencing technologies that allow for sequencing of the whole CHO genome and sophisticated bioinformatics for improving analysis of sequencing data.
This edition has reformatted worked problems; connections to online media; new problem-solving videos, online branched tutorials, online worked problems, quizzes, figure-based end-of-chapter problems, and introductory stories; updated and new animations/simulations; revised media resources; updated clicker questions; new lecture PowerPoints; new content on epigenetics, molecular genetics, conditional probability, CRISPR RNAs, long noncoding RNAs, Illumina sequencing, and evolution through changes in gene regulation; a revised section on DNA fingerprinting; and expanded discussion of the discovery of DNA structure, chromosome rearrangements, changes in chromatin structure, genome-wide association studies.
The target of this research is the epigenome, which is composed of methylated DNA, histone proteins, chromatin structure, and noncoding RNA.
"We found that stem cells have a different chromatin structure than somatic (specialized) cells.
In vitro, the nucleosome assembly of DNA containing repeating CTG triplets showed that the efficiency of nucleosome formation increased with expanded triplet blocks [16-18], suggesting that such blocks may profoundly alter local chromatin structure and repress transcription through the creation of stable nucleosomes.
Evenson will also explain his Sperm Chromatin Structure Assay, how it works and how it can help couples and their doctors determine next steps.