nucleolus

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nucleolus

 [noo-kle´o-lus] (L.)
a rounded refractile body in the nucleus of most cells, which is the site of synthesis of ribosomal RNA, becoming enlarged during periods of synthesis and smaller during quiescent periods; multiple nucleoli occur in some cells.

nu·cle·o·lus

, pl.

nu·cle·o·li

(nū-klē'ō-lŭs, -lī), Avoid the mispronunciation nucleo'lus.
1. A small, rounded mass within the cell nucleus where ribosomal ribonucleoprotein is produced; it is usually single, but there may be several not bound to membrane accessory nucleoli besides the principal one. The nucleolus is composed of a meshwork (nucleolonema) of microfilaments and granules and the pars amorpha, now shown to have microfilaments also.
2. A more-or-less central body in the vesicular nucleus of certain protozoa in which an endosome is lacking but one or more Feulgen-positive (DNA+) nucleoli are present; characteristic of certain sporozoans, flagellates, opalinids, dinoflagellates, and radiolarians among the Protozoa. The chromatin material is distributed throughout the nucleus rather than peripherally, as in the endosome type of nucleus of Entamoeba.
[L. dim of nucleus, a nut, kernel]

nucleolus

(no͞o-klē′ə-ləs, nyo͞o-)
n. pl. nucleo·li (-lī′)
A small body in the nucleus of a cell that contains protein and RNA and is the site for the synthesis of ribosomal RNA and for the formation of ribosomal subunits.

nu·cle′o·lar (-lər) adj.

nu·cle·o·lus

, pl. nucleoli (nū-klē'ŏ-lŭs, nū-klē'ō-lī)
A small, rounded mass within the cell nucleus where ribonucleoprotein is produced.
[L. dim of nucleus, a nut, kernel]

nucleolus

A small, dense rounded body found in the nucleus of most cells. The nucleolus generates RIBOSOMES and is the site of the transcription of ribosomal RNA. The size and number of nucleoli in a cell nucleus vary with the amount of protein synthesized by the cell.

nucleolus

(pl. nucleoli) an organelle found within the nuclei of EUKARYOTES, that contains RIBOSOMAL RNA and is associated with that part of the chromosome which codes for rRNA. Each nucleus contains one or more nucleoli, which appear darkly stained in preparations.