Latest revision as of 14:12, 21 February 2025

Cell Nucleus[edit]

The cell nucleus is a membrane-bound organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The nucleus maintains the integrity of these genes and controls the activities of the cell by regulating gene expression.

Structure[edit]

The nucleus is composed of several key structures:

Nuclear Envelope[edit]

The nuclear envelope is a double membrane that encloses the entire organelle and separates its contents from the cellular cytoplasm. The outer membrane is continuous with the endoplasmic reticulum.

Nuclear Pores[edit]

Nuclear pores are large protein complexes that cross the nuclear envelope, allowing the transport of molecules across the nuclear envelope. This transport includes the movement of RNA and ribosomal subunits from the nucleus to the cytoplasm and the import of proteins, carbohydrates, signaling molecules, and lipids into the nucleus.

Chromatin[edit]

Chromatin is the complex of DNA and protein found in the nucleus, which packages the DNA into a more compact, denser shape. It is divided into euchromatin and heterochromatin, which differ in their degree of condensation and transcriptional activity.

Nucleolus[edit]

The nucleolus is a region within the nucleus that is involved in the production of ribosomes. It is the site of rRNA synthesis and ribosome subunit assembly.

Nuclear Matrix[edit]

The nuclear matrix is a network of fibers found throughout the inside of a cell nucleus and is thought to provide structural support and may be involved in the regulation of gene expression.

Cajal Bodies[edit]

Cajal bodies are spherical sub-organelles found in the nucleus of proliferative cells. They are involved in the biogenesis of snRNPs and other RNA-related processes.

Function[edit]

The primary functions of the nucleus include:

Gene Expression Regulation: The nucleus controls the expression of genes by regulating the transcription of DNA into RNA.
DNA Replication: The nucleus is the site of DNA replication, where the cell's genetic material is duplicated before cell division.
RNA Processing: The nucleus is involved in the processing of pre-mRNA into mature mRNA, which is then exported to the cytoplasm for translation.

Transport Mechanisms[edit]

Diagram of the Ran-GTP cycle involved in nuclear transport.

Transport across the nuclear envelope is mediated by the nuclear pore complexes and involves a variety of transport receptors. The Ran-GTP cycle is a key regulator of nucleocytoplasmic transport.

Chromosome Territories[edit]

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Chromosome territories in a mouse cell nucleus.

Chromosome territories are regions of the nucleus preferentially occupied by particular chromosomes. This spatial organization is thought to play a role in the regulation of gene expression.

Transcription Factories[edit]

File:Basic diagram of a transcription factory during transcription.png

Diagram of a transcription factory.

Transcription factories are discrete sites within the nucleus where active transcription occurs. These factories contain clusters of RNA polymerases and associated transcription factors.

Related Pages[edit]

@@ Line 1: / Line 1: @@
-{{Short description|The control center of a eukaryotic cell}}
+= Cell Nucleus =
 The '''cell nucleus''' is a membrane-bound organelle found in [[eukaryotic cells]]. It contains most of the cell's genetic material, organized as multiple long linear [[DNA]] molecules in complex with a large variety of proteins, such as [[histones]], to form [[chromosomes]]. The nucleus maintains the integrity of these genes and controls the activities of the cell by regulating gene expression.
-==Structure==
+== Structure ==
-The nucleus is surrounded by a double membrane called the [[nuclear envelope]], which separates the contents of the nucleus from the cytoplasm. The nuclear envelope is perforated by nuclear pores that allow the transport of molecules across the nuclear envelope. The interior of the nucleus is filled with a gel-like substance called the [[nucleoplasm]], which contains the [[chromatin]] and the [[nucleolus]].
-===Nuclear Envelope===
+[[File:Diagram_human_cell_nucleus.svg|thumb|right|Diagram of a human cell nucleus.]]
-[[File:Nuclear Envelope.svg|thumb|right|Diagram of the nuclear envelope.]]
-The nuclear envelope consists of two lipid bilayer membranes, an inner and an outer membrane. The outer membrane is continuous with the [[endoplasmic reticulum]]. The space between the two membranes is called the perinuclear space.
-===Nuclear Pores===
+The nucleus is composed of several key structures:
-[[File:Nuclear Pore Complex.svg|thumb|left|Structure of a nuclear pore complex.]]
-Nuclear pores are large protein complexes that cross the nuclear envelope, allowing the transport of molecules such as [[RNA]] and proteins between the nucleus and the cytoplasm. Each pore is composed of multiple proteins known as nucleoporins.
-===Nucleoplasm===
+=== Nuclear Envelope ===
-The nucleoplasm is the semi-fluid substance within the nuclear envelope. It is similar to the cytoplasm and contains dissolved ions, molecules, and a network of fibers that help maintain the shape of the nucleus.
-===Chromatin===
+The nuclear envelope is a double membrane that encloses the entire organelle and separates its contents from the cellular cytoplasm. The outer membrane is continuous with the [[endoplasmic reticulum]].
-Chromatin is the complex of DNA and protein found in the nucleus. It exists in two forms: [[euchromatin]], which is less condensed and transcriptionally active, and [[heterochromatin]], which is more condensed and transcriptionally inactive.
-===Nucleolus===
+=== Nuclear Pores ===
-[[File:Nucleolus.svg|thumb|right|Diagram of the nucleolus.]]
-The nucleolus is a dense region within the nucleus where [[ribosomal RNA]] (rRNA) is synthesized and combined with proteins to form ribosomal subunits. These subunits are then transported out to the cytoplasm where they combine to form functional ribosomes.
-==Function==
+[[File:NuclearPore_crop.svg|thumb|left|Diagram of a nuclear pore complex.]]
-The primary function of the nucleus is to store and protect the cell's genetic material. It also regulates gene expression and mediates the replication of DNA during the cell cycle.
-===Gene Expression===
+Nuclear pores are large protein complexes that cross the nuclear envelope, allowing the transport of molecules across the nuclear envelope. This transport includes the movement of [[RNA]] and [[ribosomal subunits]] from the nucleus to the cytoplasm and the import of proteins, carbohydrates, signaling molecules, and lipids into the nucleus.
-The nucleus controls gene expression by regulating the transcription of DNA into RNA. This process is mediated by [[RNA polymerase]] and various transcription factors.
-===DNA Replication===
+=== Chromatin ===
-During the [[cell cycle]], the nucleus is responsible for the replication of DNA. This ensures that each daughter cell receives an identical set of genetic information.
-==Cell Cycle and Division==
+Chromatin is the complex of DNA and protein found in the nucleus, which packages the DNA into a more compact, denser shape. It is divided into [[euchromatin]] and [[heterochromatin]], which differ in their degree of condensation and transcriptional activity.
-The nucleus plays a crucial role in the [[cell cycle]], particularly during [[mitosis]] and [[meiosis]]. During mitosis, the nuclear envelope breaks down, allowing the chromosomes to be separated into two new nuclei. In meiosis, the nucleus undergoes two rounds of division to produce gametes with half the number of chromosomes.
+=== Nucleolus ===
+The nucleolus is a region within the nucleus that is involved in the production of [[ribosomes]]. It is the site of [[rRNA]] synthesis and ribosome subunit assembly.
+=== Nuclear Matrix ===
+The nuclear matrix is a network of fibers found throughout the inside of a cell nucleus and is thought to provide structural support and may be involved in the regulation of gene expression.
+=== Cajal Bodies ===
+[[File:Cajal-Body-Overview.svg|thumb|right|Overview of a Cajal body.]]
+Cajal bodies are spherical sub-organelles found in the nucleus of proliferative cells. They are involved in the biogenesis of [[snRNPs]] and other RNA-related processes.
+== Function ==
+The primary functions of the nucleus include:
+* '''Gene Expression Regulation''': The nucleus controls the expression of genes by regulating the transcription of DNA into RNA.
+* '''DNA Replication''': The nucleus is the site of DNA replication, where the cell's genetic material is duplicated before cell division.
+* '''RNA Processing''': The nucleus is involved in the processing of pre-mRNA into mature mRNA, which is then exported to the cytoplasm for translation.
+== Transport Mechanisms ==
+[[File:RanGTPcycle.png|thumb|left|Diagram of the Ran-GTP cycle involved in nuclear transport.]]
+Transport across the nuclear envelope is mediated by the nuclear pore complexes and involves a variety of transport receptors. The Ran-GTP cycle is a key regulator of nucleocytoplasmic transport.
+== Chromosome Territories ==
+[[File:MouseChromosomeTerritoriesBMC_Cell_Biol6-44Fig2e.jpg|thumb|right|Chromosome territories in a mouse cell nucleus.]]
+Chromosome territories are regions of the nucleus preferentially occupied by particular chromosomes. This spatial organization is thought to play a role in the regulation of gene expression.
+== Transcription Factories ==
+[[File:Basic_diagram_of_a_transcription_factory_during_transcription.png|thumb|left|Diagram of a transcription factory.]]
+Transcription factories are discrete sites within the nucleus where active transcription occurs. These factories contain clusters of RNA polymerases and associated transcription factors.
+== Related Pages ==
-==Related pages==
 * [[Eukaryotic cell]]
-* [[Chromosome]]
 * [[DNA replication]]
 * [[Gene expression]]
-* [[Mitosis]]
+* [[Ribosome]]
-* [[Meiosis]]
+* [[Chromosome]]
 [[Category:Cell biology]]
 [[Category:Organelles]]

Cell nucleus: Difference between revisions