Cell nucleus

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Cell nucleus

The largest of the membrane-bounded organelles which characterize eukaryotic cells; it is thought of as the control center since it contains the bulk of the cell's genetic information in the form of deoxyribonucleic acid (DNA). The nucleus has two major functions: (1) It is the site of synthesis of ribonucleic acid (RNA), which in turn directs the formation of the protein molecules on which all life depends; and (2) in any cell preparing for division, the nucleus precisely duplicates its DNA for later distribution to cell progeny. See Deoxyribonucleic acid (DNA), Eukaryotae, Ribonucleic acid (RNA)

The diameter of nuclei ranges from 1 micrometer in intracellular parasites and yeast cells to several millimeters in some insect sperm. Spherical or ellipsoidal nuclei are found in most cell types, although occasionally spindle-shaped, lobulated, disc-shaped, or cup-shaped nuclei may be observed. Although nuclear size and shape are somewhat consistent features of a particular cell type, these features are more variable in cancer cells. In addition, tumor cell nuclei are characterized by indentation, furrowing, elongation, and budding.

The nucleus is bounded by a double membrane (the nuclear envelope) and contains several major components: chromatin, which is composed of DNA and chromosomal proteins; the nucleolus, which is the site of ribosomal RNA (rRNA) synthesis; and nucleoplasmic fibrils and granules, some of which are involved in the processing and transport of messenger RNA out of the nucleus (see illustration). The constituents of the nucleus are contained within a framework referred to as the nuclear matrix.

Transmission electron micrograph of a thin section of a rat liver cell nucleusenlarge picture
Transmission electron micrograph of a thin section of a rat liver cell nucleus
References in periodicals archive ?
In the lab, Baia knocked down the amount of YAP1 in cell nuclei and found that tumor proliferation went down.
Immunohistochemical studies demonstrated p53 protein localization in cell nuclei of both tumors, as well as in the adjacent normal-appearing adrenal cortical cell nuclei.
The report also stated that archaea and bacteria live symbiotically with eukaryotes to form cell nuclei and thus produce eukaryotic organisms in ''mosaic structure.
The cell nuclei have a homogenous "ground-glass" appearance and may contain Cowdry type A intranuclear inclusions.
Full-term development of mice from enucleated oocytes injected with cumulus cell nuclei.
They found that if the muscle cell nuclei outnumbered the skin cell nuclei, the skin nuclei began to express muscle-specific genes within a few hours of fusion.
Until now, scientists had extracted small DNA segments from Neandertal bones, mainly from mitochondria outside cell nuclei (SN: 4/1/00, p.
The experiments involved the separate introduction of sheep, pig, rat and rhesus monkey skin cell nuclei into cow cells whose nuclei had been removed.
The inventions described in the intellectual property portfolio, which are covered by issued and pending patents, cover techniques for the reprogramming of somatic cell nuclei, including the use of extracts for the reprogramming of somatic cell nuclei, for the generation of cloned and/or transgenic animals and for the reprogramming of human cells.
Despite examining 10 scenarios of inheritance, both for mitochondrial DNA and DNA from cell nuclei, the researchers were unable to explain genetically the observed female-biased pattern of sponge carrying.
The hypocellular Antoni B area has a varying degree of cell pleomorphism; irregular cell types are scattered in loose connective tissue, and there is no definable palisading of tumor cell nuclei.
With precision & reliability, a non-contact laser beam will select, dissect and catapult selected living cell areas, cell nuclei or chromosomes directly into the cap of a common microphage tube for subsequent evaluation by PCR without danger of contamination.