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 ?
Nuclear protein samples were extracted from frozen mouse tissues using methods adopted from a previous report (Vogel et al.
A genomic fragment of the larger sperm nuclear protein (P1) was obtained from S.
Nuclear protein extraction, western blotting, and co-immunoprecipitation analyses
Carcinomas of the upper aerodigestive tract with rearrangement of the nuclear protein of the testis (NUT) gene (NUT midline carcinomas).
Chemical differentiation of nuclear proteins during spermatogenesis in the salmon.
In some experiments, nuclear extracts were incubated with a 50 molar excess of unlabeled probe or an unlabeled probe from a different binding motif to examine the specificity of nuclear protein binding to the oligonucleotides.
In addition to its role in metabolic processes, Cr has been shown to affect nuclear protein (Weser and Koolman, 1969) and RNA synthesis (Okada et al.
Binding occurred with nuclear proteins from hematopoietic cells, but not with nuclear proteins from fibroblast cells.
Translocated p26 is believed to function as a molecular chaperone for nuclear proteins, including lamins--major nuclear proteins--probably in association with hsp70 (Willsie and Clegg, 2002).
The hypothetical model included genes that produce three alcohol dehydrogenases, a cytochrome P450 enzyme, retinoic acid binding proteins and receptors, and four nuclear proteins.
32]P]-labeled-oligonucleotide to nuclear proteins was inhibited completely by unlabeled oligonucleotide at 5 [Mu]g, suggesting that nuclear proteins bind specifically to the oligonucleotide (Figure 3, A and B).
The resulting supernatant was used as soluble nuclear proteins.

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