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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 is the largest of the discrete densely stained, membraneless structures known as nuclear bodies found in the nucleus. It forms around tandem repeats of rDNA, DNA coding for ribosomal RNA (rRNA). These regions are called nucleolar organizer regions (NOR). The main roles of the nucleolus are to synthesize rRNA and assemble ribosomes ...
nucleolus An organelle within the nucleus of eukaryotic cells which is composed of proteins, DNA, and RNA and serves as the site of ribosome synthesis. nucleoplasm. Also karyoplasm. All of the material enclosed within the nucleus of a cell by the nuclear envelope, analogous to the cytoplasm enclosed by the main cell membrane.
The organelles and other structures within the cytoplasm and nucleoplasm are organized by protein filaments within their respective compartments. The cytoplasm contains the cytoskeleton, a network of protein filaments found in all cells, while the nucleoplasm is believed to contain the nuclear matrix, a hypothetically analogous network of ...
In fact, DNA analysis of these two types of domains have shown that many sequences overlap, indicating that certain regions may switch between lamina-binding and nucleolus-binding. [35] NADs are associated with nucleolus function. The nucleolus is the largest sub-organelle within the nucleus and is the principal site for rRNA transcription.
In terms of protein synthesis, the necessary organelles are relatively near one another. The nucleolus within the nuclear envelope is the location of ribosome synthesis. The destination of synthesized ribosomes for protein translation is rough endoplasmic reticulum (rough ER), which is connected to and shares the same membrane with the nucleus.
Nucleolus organizer regions (NORs) are chromosomal regions crucial for the formation of the nucleolus. In humans, the NORs are located on the short arms of the acrocentric chromosomes 13, 14, 15, 21 and 22, the genes RNR1, RNR2, RNR3, RNR4, and RNR5 respectively. [1] These regions code for 5.8S, 18S, and 28S ribosomal RNA. [1]
In biochemistry, biomolecular condensates are a class of membrane-less organelles and organelle subdomains, which carry out specialized functions within the cell. Unlike many organelles, biomolecular condensate composition is not controlled by a bounding membrane.