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

noun

• 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

The secret to cellular youth may depend on keeping the nucleolus -- a condensed structure inside the nucleus of a cell -- small, according to Weill Cornell Medicine investigators.

From Science Daily • Nov. 25, 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

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

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

From Textbooks • Jun. 9, 2022

In brief, then, a cell is a mass of nucleated protoplasm; the nucleus may have a nucleolus, and the cell may be limited by a cell wall.

From A Practical Physiology by Blaisdell, Albert F.