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.

---

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

---

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.

---

Other Word Forms

Derived Forms

• nucleolar
  adjective

Inflected Forms

Nouns

• nucleoli
  plural

---

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

See Examples For:

nucleolus nucleoli

"I was excited that we could connect the structure of the nucleolus with the repair process in a way that could be conserved from yeast to humans," said Dr. Gutierrez.

From Science Daily ● Nov. 25, 2024

As a result, any transgene inserted into the rDNA region of the genome would be treated with kid gloves inside the nucleolus.

From Science Daily ● Feb. 20, 2024

All of these stubby arms huddle together to form a structure called the nucleolus, in which DNA is transcribed into ribosomal RNA, which then folds into the ribosomal machinery that makes proteins.

From Science Daily ● Feb. 20, 2024

The nucleus’s nucleolus is the site of ribosome assembly.

From Textbooks ● Jun. 9, 2022

Various forms assumed by the combined nucleolus and element x; last figure from a giant cell.

From Studies in Spermatogenesis Part I by Nettie Maria Stevens

Older APOE2 knock-in mice had smaller nucleoli, higher levels of the nuclear scaffolding protein Lamin A/C, and better-preserved heterochromatin in the hippocampus than mice carrying APOE3 or APOE4.

From Science Daily ● Jul. 24, 2026

The researchers discovered that tethering the nucleolus was enough to keep it compact, and small nucleoli delayed aging to about the same extent as calorie restriction.

From Science Daily ● Nov. 25, 2024

The community of molecules that come together enables emergent properties in the condensates, like internal pH in nucleoli.

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

Random Word

Spin the wheel and learn a new word!

---