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Subject - Biochemistry, Cell Biology

The nucleus (from Latin nucleus "kernel") is an organelle found in the cytoplasm of eukaryotes. It is where the chromosomes are located and processes like DNA replication, DNA transcription, mRNA splicing, and manufacture of the ribosomal units occur. Whereas eukaryotes (from Greek eu "good" and karyon "kernel") like animals, plants, and fungi have a true nucleus, prokaryotes (bacteria, blue-green algae, archaea) only have nucleoid regions, in which the nucleic acids are found. The nucleus is separated from the cytoplasm by a porous nuclear membrane, through which proteins can enter the nuclear plasma and mRNA transcripts can leave it. During cell division processes like mitosis and meiosis, the nuclear membrane is temporarily dissolved.

Eukaryotic cells are generally mononuclear, but there are exceptions like the anucleate erythrocytes or the polynuclear vegetative bodies of lower fungi.

See also: eukaryotes , organelles

Recommended Learning Units

Cell Structure and Cell OrganellesLevel 160 min.

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Cytology is introduced by means of illustrations, animations, and a comprehensive collection of references and selected links.