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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 ?
Once RA binds to RAR, the repressor complex is replaced with the activator complex, inducing a relaxed chromatin structure through H3K9ac.
The chromatin structure of the spermatozoa was evaluated using acridine orange according to a methodology proposed by Bochenek et al.
Fazzio will explore the link between chromatin structures and gene expression in stem cells.
Sperm chromatin structure assay parameters are not related to fertilization rates, embryo quality, and pregnancy rates in in vitro fertilization and intracytoplasmic sperm injection, but might be related to spontaneous abortion rates.
The aim of this article is to provide an overview of the main plant hormones signal transduction pathways, to present plant histones in comparison to their animal counterparts and to discuss the evidence accumulated during the last few years concerning the effect of plant hormone signaling on chromatin structure and function and also the influence of distinct chromatin patterns on plant hormone responses.
The relationship between chromatin structure and DNA damage in mammalian spermatozoa.
Baf53b, and the nBAF complex, physically open the chromatin structure so specific genes required for long-term memory formation are turned on.
Studies using a diverse range of model organisms have led to the conclusion that epigenetic modifications to the chromatin structure provide a plausible link between exposure to environmental substances that can harm the developing fetus (i.
The major functional categories these genes are involved in have been identified: cell receptor signaling, chromatin structure and transcription, control of cell death, cell cycle, Wnt/beta-catenin signaling, and lipid signaling.
Chromatin structure data can be obtained within six hours from as few as 50,000 cultured cells, without the need for nuclei isolation.
She and Georgel, an expert in changes in chromatin structure, collaborated on preliminary studies, which demonstrated a change in chromatin structure associated with changed gene expression that could reduce risk for breast cancer.