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The cell nucleus (from Latin nucleus or nuculeus ' kernel, seed '; pl.: nuclei) is a membrane-bound organelle found in eukaryotic cells.Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoclasts have many.
The cell on the left is going through mitosis and its chromosomes have condensed. Cell nucleus: A cell's information center, the cell nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomes, and is the place where almost all DNA replication and RNA synthesis (transcription) occur.
Nuclear DNA and mitochondrial DNA differ in many ways, starting with location and structure. Nuclear DNA is located within the nucleus of eukaryote cells and usually has two copies per cell while mitochondrial DNA is located in the mitochondria and contains 100–1,000 copies per cell.
Eukaryotic cells have a variety of internal membrane-bound structures, called organelles, and a cytoskeleton which defines the cell's organization and shape. The nucleus stores the cell's DNA, which is divided into linear bundles called chromosomes; [18] these are separated into two matching sets by a microtubular spindle during nuclear ...
There is an immense size variation in vertebrate red blood cells, as well as a correlation between cell and nucleus size. Mammalian red blood cells, which do not contain nuclei, are considerably smaller than those of most other vertebrates. [10] Mature red blood cells of birds have a nucleus, however in the blood of adult females of penguin ...
The actual shape of the nuclear envelope is irregular. It has invaginations and protrusions and can be observed with an electron microscope. A volumetric surface render (red) of the nuclear envelope of one HeLa cell. The cell was observed in 300 slices of electron microscopy, the nuclear envelope was automatically segmented and rendered. One ...
The nucleolus (/ nj uː ˈ k l iː ə l ə s, ˌ nj uː k l i ˈ oʊ l ə s /; pl.: nucleoli /-l aɪ /) is the largest structure in the nucleus of eukaryotic cells. [1] It is best known as the site of ribosome biogenesis. The nucleolus also participates in the formation of signal recognition particles and plays a role in the cell's response to ...
The cell is the fundamental unit of structure and function in all living organisms. [14] The activity of an organism depends on the total activity of independent cells. [15] Energy flow (metabolism and biochemistry) occurs within cells. Cells contain DNA which is found specifically in the chromosome and RNA found in the cell nucleus and ...