nucleoid

American  

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

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

See Examples For:

nucleoid

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 DNA of prokaryotes is organized into a circular chromosome supercoiled in the nucleoid region of the cell cytoplasm.

From Textbooks ● Jun. 9, 2022

Typical cells in Archaea and Bacteria contain a cell wall, nuclear membranes, nucleoid region and often a capsule, flagellum, and pili but in some instances different chemical compounds make them.

From Textbooks ● Jun. 9, 2022

Figure 9.6 A eukaryote contains a well-defined nucleus, whereas in prokaryotes, the chromosome lies in the cytoplasm in an area called the nucleoid.

From Textbooks ● Apr. 25, 2013

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