Mathematical modeling shows why animals see at night

Nocturnal and diurnal mammals see the same—but only for a brief time. When mice are born, the chromatin in the cells of their eyes has a diurnal structure. Day by day, the layout of this chromatin slowly inverts, allowing ...

Upcycling of proteins protects DNA from parasites

Of the three billion base pairs in the human genome, less than two percent contain the information encoding the ~20,000 proteins. That is, because at least half of our genetic material originated from selfish genetic elements ...

Gatekeepers of the genome

Transcription factors control gene activation in cells. By binding to specific segments of DNA, they enable the blueprints that code for cellular proteins to be produced. But how are such factors themselves regulated?

New insight into microRNA function can give gene therapy a boost

Scientists at the University of Eastern Finland and the University of Oxford have shown that small RNA molecules occurring naturally in cells, i.e. microRNAs, are also abundant in cell nuclei. Previously, microRNAs were mainly ...

New function for the nucleolus

The nucleolus is a well-known structure in the cell nucleus that is easily visible under a light microscope. This nuclear structure is known to be the site of ribosome production. A new study shows that the nucleolus is also ...

Applying the Goldilocks principle to DNA structure

The Goldilocks of fairy-tale fame knew something about porridge. It needed to be just right—neither too hot nor too cold. Same with furniture—neither too hard nor too soft. In a different context, scientists at UC San ...

Research uncovers elusive process essential to plant greening

Despite how essential plants are for life on Earth, little is known about how parts of plant cells orchestrate growth and greening. By creating mutant plants, UC Riverside researchers have uncovered a cellular communication ...

How the cell protects itself

The cell contains transcripts of genetic material, which migrate from the cell nucleus to another part of the cell. This movement protects the genetic transcripts from the recruitment of "spliceosomes." If this protection ...

What organizes the genome in the nucleus?

Spatial separation of active from inactive fractions of the genome in the cell nucleus is crucial for gene expression control. A new study uncovers leading mechanisms of such separation and turns our picture of the nucleus ...

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Cell nucleus

In cell biology, the nucleus (pl. nuclei; from Latin nucleus or nuculeus, or kernel), also sometimes referred to as the "control center", is a membrane-enclosed 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 genes within these chromosomes are the cell's nuclear genome. The function of the nucleus is to maintain the integrity of these genes and to control the activities of the cell by regulating gene expression--the nucleus is therefore the control center of the cell.

The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and separates its contents from the cellular cytoplasm, and the nuclear lamina, a meshwork within the nucleus that adds mechanical support, much like the cytoskeleton supports the cell as a whole. Because the nuclear membrane is impermeable to most molecules, nuclear pores are required to allow movement of molecules across the envelope. These pores cross both of the membranes, providing a channel that allows free movement of small molecules and ions. The movement of larger molecules such as proteins is carefully controlled, and requires active transport regulated by carrier proteins. Nuclear transport is crucial to cell function, as movement through the pores is required for both gene expression and chromosomal maintenance.

Although the interior of the nucleus does not contain any membrane-bound subcompartments, its contents are not uniform, and a number of subnuclear bodies exist, made up of unique proteins, RNA molecules, and particular parts of the chromosomes. The best known of these is the nucleolus, which is mainly involved in the assembly of ribosomes. After being produced in the nucleolus, ribosomes are exported to the cytoplasm where they translate mRNA.

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