nucleolus

American  

[noo-klee-uh-luhs, nyoo-] / nuˈkli ə ləs, nyu- /

noun

Cell Biology.

plural

nucleoli

1. a conspicuous, rounded body within the nucleus of a cell.

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nucleolus British  

/ ˌnjuːklɪˈəʊləs /

noun

1. Also called: nucleole.  a small rounded body within a resting nucleus that contains RNA and proteins and is involved in the production of ribosomes

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nucleolus Scientific  

/ no̅o̅-klē′ə-ləs /

plural

nucleoli

1. A small, typically spherical granular body located in the nucleus of a eukaryotic cell, composed largely of protein and RNA. When the cell is not undergoing division, loops of DNA from one or more chromosomes extend into the nucleolus and direct the synthesis of ribosomal RNA and the formation of ribosomes. The ribosomes are eventually transferred out of the nucleus via pores in the nuclear envelope into the cytoplasm.

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Other Word Forms

• nucleolar adjective

Etymology

Origin of nucleolus

1835–45; < Late Latin: small kernel, equivalent to nucle ( us ) kernel ( see nucleus) + -olus -ole ¹

Explanation

A nucleolus is the largest structure within the nucleus of a eukaryotic cell. It's the job of a nucleolus to make RNA and ribosomes. In a eukaryote, a cell whose nucleus is contained within a membrane, the nucleolus plays a vital role. It's here that ribosomes, tiny cell machines that produce important proteins, are made. RNA — which works by taking the information in DNA and translating it into proteins — also comes from the nucleolus. Nucleolus basically means "smaller nucleus," from a Latin word meaning "little nut."

Example Sentences

"The advantage of our system is that we could isolate the nucleolus size from all of the other effects of anti-aging strategies," Dr. Gutierrez said.

From Science Daily • Nov. 25, 2024

It's as if the nucleolus becomes leaky, letting in molecules that can wreak havoc on the fragile rDNA.

From Science Daily • Nov. 25, 2024

Within the nucleolus, rDNA transcription is highly regulated, and the genes undergo quick repairs, since any rDNA breaks, if left to propagate, could shut down protein production.

From Science Daily • Feb. 20, 2024

The nucleolus is a condensed region of chromatin where ribosome synthesis occurs.

From Textbooks • Jun. 9, 2022

There is nothing in the resting nucleus of the spermatogonia which would suggest either a nucleolus or an accessory chromosome.

From Studies in Spermatogenesis Part I by Stevens, Nettie Maria