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 ...

Mammoth moves: frozen cells come to life, but only just

A team of scientists in Japan has successfully coaxed activity from 28,000-year-old cells from a frozen mammoth implanted into mouse cells, but the woolly mammal is unlikely to be walking among us soon.

Nucleus-specific X-ray stain for 3-D virtual histology

Histology is used to identify structural details of tissue at the microscale in the pathology lab, but analyses remain two-dimensional (2D) as they are limited to the same plane. Nondestructive 3D technologies including X-ray ...

Genome-wide rules of nucleosome phasing in drosophila

LMU researchers have, for the first time, systematically determined the positioning of the packing units of the fruit fly genome and discovered a new protein that defines their relationship to the DNA sequence.

Plasma from lasers can shed light on cosmic rays, solar eruptions

Lasers that generate plasma can provide insight into bursts of subatomic particles that occur in deep space, scientists have found. Such findings could help scientists understand cosmic rays, solar flares and solar eruptions—emissions ...

DNA dominos on a chip

Normally, individual molecules of genetic material repel each other. However, when space is limited DNA molecules must be packed together more tightly. This case arises in sperm, cell nuclei and the protein shells of viruses. ...

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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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