nucleolus

American  

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

noun

Cell Biology.

• nucleoli
  plural

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 /

• nucleoli
  plural

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

Derived Forms

• nucleolar
  adjective

Inflected Forms

Nouns

• nucleoli
  plural

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Etymology

Origin of nucleolus

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

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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

See Examples For:

nucleolus nucleoli

"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

Also, when the structure is large, proteins and other factors that are usually excluded from the nucleolus are no longer kept out.

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

If the nucleolus were not able to carry out its function, what other cellular organelles would be affected?

From Textbooks ● Jun. 9, 2022

If the body be studied in its development, it is found to originate from a single mass of nucleated protoplasm, a single cell with a nucleus and nucleolus.

From A Practical Physiology by Albert F. Blaisdell

They also had smaller nucleoli and better-preserved nuclear architecture, both signs that the cells were maintaining a healthier internal structure.

From Science Daily ● Jul. 24, 2026

Dr. Tyler and postdoctoral fellow Dr. J. Ignacio Gutierrez, the first author of the paper, suspected that keeping nucleoli small could delay aging.

From Science Daily ● Nov. 25, 2024

This organization gives rise to unique pH profiles within nucleoli, which they measured and compared with the pH of nearby non-nucleolar condensates including nuclear speckles and Cajal bodies.

From Science Daily ● Mar. 18, 2024

The nucleus contains one or more nucleoli, which serve as sites for ribosome synthesis.

From Textbooks ● Jun. 19, 2013

Within the nucleus are often to be found one or two nucleoli with a relatively thick and deeply stained membrane.

From Histology of the Blood Normal and Pathological by W. Myers

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