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The nucleoid (meaning nucleus-like) is an irregularly shaped region within the prokaryotic cell that contains all or most of the genetic material. [1] [2] [3] The chromosome of a typical prokaryote is circular, and its length is very large compared to the cell dimensions, so it needs to be compacted in order to fit.
Diagram of a prokaryotic cell, a bacterium with a flagellum. A prokaryote (/ p r oʊ ˈ k ær i oʊ t,-ə t /; less commonly spelled procaryote) [1] is a single-celled organism whose cell lacks a nucleus and other membrane-bound organelles. [2]
The DNA of a prokaryotic cell consists of a single circular chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid. Most prokaryotes are the smallest of all organisms, ranging from 0.5 to 2.0 μm in diameter. [1] [page needed] A prokaryotic cell has three regions:
It is present in most cells, with a few exceptions, for example, red blood cells. Histones are responsible for the first and most basic unit of chromosome organization, the nucleosome . Eukaryotes ( cells with nuclei such as those found in plants, fungi, and animals) possess multiple large linear chromosomes contained in the cell's nucleus.
Although prokaryotic organisms do not possess a membrane-bound nucleus like eukaryotes, they do contain a nucleoid region in which the main chromosome is found. Extrachromosomal DNA exists in prokaryotes outside the nucleoid region as circular or linear plasmids.
The prokaryotic cytoskeleton is the collective name for all structural filaments in prokaryotes. It was once thought that prokaryotic cells did not possess cytoskeletons , but advances in imaging technology and structure determination have shown the presence of filaments in these cells. [ 9 ]
The prokaryotic cytoskeletal elements are matched with their eukaryotic homologue and hypothesized cellular function. [1] The prokaryotic cytoskeleton is the collective name for all structural filaments in prokaryotes. [2] Some of these proteins are analogues of those in eukaryotes, while others are unique to prokaryotes.
They are most commonly found as small circular, double-stranded DNA molecules in bacteria; however, plasmids are sometimes present in archaea and eukaryotic organisms. [1] [page needed] [2] Plasmids often carry useful genes, such as those involved in antibiotic resistance, virulence, [3] [4] [5] secondary metabolism [6] and bioremediation.