A membrane-enclosed organelle found in eukaryotic cells.

Eukaryotes usually have a single nucleus.

A few cell types, such as mammalian red blood cells, have no nuclei.

A few cells including osteoclasts have many nuclei.

Cell nuclei contain most of the cell’s genetic material.

The average diameter of the nucleus is approximately 6 micrometres (µm), which occupies about 10% of the total cell volume.

The viscous liquid within it is called nucleoplasm and is similar in composition to the cytosol found outside the nucleus.

The nucleus appears as a dense, roughly spherical or irregular organelle.

The composition by dry weight of the nucleus is approximately: DNA 9%, RNA 1%, Histone Protein 11%, Residual Protein 14%, Acidic Proteins 65%.

The cell genetic material is organized as multiple long linear DNA molecules in a complex with a large variety of proteins, such as histones, to form chromosomes.

The genes within chromosomes are the cell’s nuclear genome.

The cell’s genome promotes cell function.

The nucleus maintains the genetic integrity and controls the activities of the cell by regulating gene expression.

It is the control center of the cell.

The nucleus is made up of the nuclear envelope, a double membrane that encloses it and isolates its contents from the cellular cytoplasm, and the nuclear matrix, which is a network within the nucleus that adds mechanical support.

The nuclear envelope, also. known as nuclear membrane, consists of two cellular membranes.

The nuclear envelope allows the nucleus to control its contents, and separate them from the rest of the cytoplasm where necessary.

There is an inner and an outer membrane, arranged parallel to one another and separated by 10 to 50 nanometers.

The nuclear envelope completely encloses the nucleus and separates the cell’s genetic material from the surrounding cytoplasm.

The nuclear envelope is a barrier to prevent macromolecules from diffusing freely between the nucleoplasm and the cytoplasm.

The nuclear envelope is impermeable to large molecules.

Nuclear pores are therefore required to regulate nuclear transport of molecules across the nuclear envelope.

The pores provide a channel through which larger molecules must be actively transported by carrier proteins while allowing free movement of small molecules and ions.

Movement through the pores of large molecules such as proteins and RNA is required for both gene expression and the maintenance of chromosomes.

The contents of the interior of the nucleus does not contain membrane-bound subcompartments, it has a number of sub-nuclear bodies, made up of unique proteins, RNA molecules, and particular parts of the chromosomes.

The nucleolus is the major interior body and it is mainly involved in the assembly of ribosomes.

The main function of the cell nucleus is to control gene expression and mediate the replication of DNA during the cell cycle.

The nucleus is an organelle fully enclosed nuclear membrane, it contains the majority of the cell’s genetic material.

This material is organized as DNA molecules, along with a variety of proteins, to form chromosomes.

After being produced in the nucleolus,

Ribosomes are produced in the nucleolus and exported to the cytoplasm where they translate messenger RNA.

The nucleus may be lobulated as a bi-lobed, tri-lobed or multi-lobed organelle, in granulocytes.

The outer nuclear membrane is continuous with the membrane of the rough endoplasmic reticulum (RER)

The outer nuclear membrane is studded with ribosomes.

The space between the inner and outer membranes is called the perinuclear space and is continuous with the rough endoplasmic reticulum lumen.

Nuclear pores provide aqueous channels through the envelope.

The nucleus has about 3000 to 4000 pores throughout its envelope.

The nuclear pores are composed of multiple proteins, ref2241ed to as nucleoporins.

Each pore contains an eightfold-symmetric ring-shaped structure at a position where the inner and outer membranes fuse.

The nuclear pores are about 125 million daltons in molecular weight, are 100 nm in total diameter and consist of several hundred proteins

Molecules that can freely diffuse are only about 9 nm wide, due to the presence of regulatory systems within the center of the nuclear pore.

The nuclear pore selectively allows the passage of small water-soluble molecules, while preventing larger molecules, such as nucleic acids and larger proteins, from inappropriately entering or exiting the nucleus.

Large molecules must be actively transported into the nucleus.

A nuclear basket attached to the ring extends into the nucleoplasm, and a series of filamentous extensions that reach into the cytoplasm.

Most proteins, ribosomal subunits, and some DNAs are transported by the karyopherin family of transport factors, through the pore complexes.

Karyopherins that mediate movement into the nucleus are also called importins.

Karyopherins that mediate movement out of the nucleus are called exportins.

Small lipid-soluble molecules and steroid hormones involved in intercellular signaling, can diffuse through the cell membrane and into the cytoplasm, where they bind nuclear receptor proteins that are trafficked into the nucleus.

The nuclear lamina, composed mostly of lamin proteins, provides structural support for the nuclear envelope and anchoring sites for chromosomes and nuclear pores.

Mutations in lamin genes leading to defects in filament assembly cause a group of rare genetic disorders known as laminopathies, the most notable of which is progeria.

The cell nucleus contains the majority of the cell’s genetic material.

It contains chromosomes which are multiple linear DNA molecules organized into structures.

Approximately two meters of DNA is present in each cell.

Most of the cell cycle these chromosomes are organized in a DNA-protein complex known as chromatin.

During cell division the chromatin form chromosomes.

A small fraction of the cell’s genes are located instead in the mitochondria.

There are two types of chromatin: Euchromatin is the less compact DNA form, and contains genes that are frequently expressed by the cell, and heterochromatin, is the more compact form, and contains DNA that is infrequently transcribed.

Antibodies to types of chromatin organization, in particular, nucleosomes, have been associated with a number of autoimmune diseases, such as systemic lupus erythematosus.

These antibodies are known as anti-nuclear antibodies.


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