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 ?
Most HDACs are activated in the cell nucleus but HDAC6 mainly affect the cell function outside the cell nucleus.
The mitochondria contain around 13 genes compared with an estimated 23,000 in the cell nucleus.
Strands of DNA in the cell nucleus are millions of times longer than those in the mitochondrion, so the project may take a couple of years.
Eighteen chapters review the literature regarding the ultrastructure of chromosome territories within the cell nucleus, the organization of the genome for its duplication and spatio-temporal regulation of DNA replication, the molecular machineries of cell mitosis, the architecture of gene domains and epigenetic regulation, the composition of transcription factories, the cotranscriptional processing of pre-mRNAs, the nuclear duties of the nucleolus, the structure of PML nuclear bodies and their dynamic protein constituents, the structure and functions of the Cajal Body, the interchromosomal domain compartment, the association of nuclear structure and function with various diseases, and a small group of new live cell and fluorescence imaging techniques.
Once synthesized, retinoic acid enters the cell nucleus.
Blastocyst: After the nucleus of a somatic cell is inserted into the place of the evacuated egg cell nucleus, the resulting cell begins to grow and divide.
the transfer of a human somatic cell nucleus into a human or animal egg;
The government should ban the transplant of a cell nucleus, which carries the genetic information of a human cell, into an unfertilized egg that had its original nucleus removed, it said.
Doctors could take a skin cell nucleus and implant it in an enucleated human egg, resetting the cell's DNA.
HIV inserts its own "poisoned" genetic code in the T cell nucleus, "tricking" the cell into becoming a virus factory.
Critical to this practical research is a new understanding of how estrogens interact with genes in the cell nucleus.
For protein expression to occur in mammalian cells, messenger RNA (mRNA) must be transported from the cell nucleus, where transcription occurs, to the cytoplasm for translation into protein.