nucleoid

American  

[noo-klee-oid, nyoo-] / ˈnu kliˌɔɪd, ˈnyu- /

noun

1. the central region in a prokaryotic cell, as a bacterium, that contains the chromosomes and that has no surrounding membrane.

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adjective

1. resembling a nucleus.

Usage

What is a nucleoid? A nucleoid is the central part of a prokaryotic cell that contains genetic material. A nucleoid is found only in a prokaryotic cell, such as a single-celled bacteria. It’s integral to reproduction and genetic behavior, housing chromosomes and DNA and, in some prokaryotic cells, additional DNA called plasmids. RNA and proteins can also be found within the nucleoid area. Nucleoid can be used to describe something that resembles a nucleus (a specialized mass of protoplasm encased in a double membrane). Example: If you examine the nucleoid of the bacteria, you’ll see that it lacks a specific chromosome related to that gene in similar organisms.

Etymology

Origin of nucleoid

First recorded in 1850–55; nucle(us) + -oid

Example Sentences

Most of these bead-like sections contain a nucleoid near the center, although the structures can also form without mtDNA present.

From Science Daily • Apr. 13, 2026

The region in the cell containing this genetic material is called a nucleoid.

From Textbooks • Jun. 9, 2022

They typically have cell walls enclosing cell membranes, cytoplasm, ribosomes and a nucleoid region with chromosomes.

From Textbooks • Jun. 9, 2022

As in eukaryotes, the DNA of the nucleoid is associated with proteins that aid in packaging the molecule into a compact size.

From Textbooks • Apr. 25, 2013

Therefore, they do not have a nucleus but instead have a single chromosome—a piece of circular DNA located in an area of the cell called the nucleoid.

From Textbooks • Apr. 25, 2013