| nucleolus | <cell biology> A small dense body (sub organelle) within the nucleus of eukaryotic cells, visible by phase contrast and interference microscopy in live cells throughout interphase. Contains RNA and protein and is the site of synthesis of ribosomal RNA. The nucleolus surrounds a region of one or more chromosomes (the nucleolar organiser) in which are repeated copies of the DNA coding for ribosomal RNA. (18 Nov 1997) |
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| nucleolus organiser | <molecular biology> Loop of DNA that has multiple copies of rRNA genes. See: nucleolus. (18 Nov 1997) |
| nucleolus organiser region | The chromosome region which is active in nucleolus formation and which functions in the synthesis of ribosomal RNA. (12 Dec 1998) |
| cell nucleolus | Within most types of eukaryotic cell nucleus, a distinct region, not delimited by a membrane, in which some species of rrna (RNA, ribosomal) are synthesised and assembled into ribonucleoprotein subunits of ribosomes. In the nucleolus rrna is transcribed from a nucleolar organiser, i.e., a group of tandemly repeated chromosomal genes which encode rrna and which are transcribed by RNA polymerase I. (12 Dec 1998) |
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| granular component of nucleolus | Area of nucleolus that appears granular in the electron microscope and contains 15nm diameter particles that are maturing ribosomes. In contrast to the pale staining and fibrillar areas. (18 Nov 1997) |
| chromatin nucleolus | <cell biology> The central portion of a cells nucleus that typically contains a glob of heterochromatin. Origin: Gr. Soma = body (09 Oct 1997) |
| false nucleolus | <cell biology> The central portion of a cells nucleus that typically contains a glob of heterochromatin. Origin: Gr. Soma = body (09 Oct 1997) |