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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.
Cells are broadly categorized into two types: eukaryotic cells, which possess a nucleus, and prokaryotic cells, which lack a nucleus but have a nucleoid region. Prokaryotes are single-celled organisms such as bacteria, whereas eukaryotes can be either single-celled, such as amoebae, or multicellular, such as some algae, plants, animals, and fungi.
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; however, plasmids are sometimes present in archaea and eukaryotic organisms.
Genomic DNA is tightly and orderly packed in the process called DNA condensation, to fit the small available volumes of the cell. In eukaryotes, DNA is located in the cell nucleus, with small amounts in mitochondria and chloroplasts. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid. [97]
Eukaryotic cells are some 10,000 times larger than prokaryotic cells by volume, have their DNA organised in a nucleus, and contain membrane-bound organelles. [ 49 ] The division between prokaryotes and eukaryotes has been considered the most important distinction or difference among organisms.
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 cell nucleus (from Latin nucleus or nuculeus ' kernel, seed '; pl.: nuclei) is a membrane-bound organelle found in eukaryotic cells.Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoclasts have many.
Prokaryotic cells have entirely different structures for organizing their DNA (the prokaryotic chromosome equivalent is called a genophore and is localized within the nucleoid region). The overall structure of the chromatin network further depends on the stage of the cell cycle.