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The term plasmid was coined in 1952 by the American molecular biologist Joshua Lederberg to refer to "any extrachromosomal hereditary determinant." [11] [12] The term's early usage included any bacterial genetic material that exists extrachromosomally for at least part of its replication cycle, but because that description includes bacterial viruses, the notion of plasmid was refined over time ...
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 cellular components of prokaryotes are not enclosed in membranes within the cytoplasm, like eukaryotic organelles. Bacteria have microcompartments, quasi-organelles enclosed in protein shells such as encapsulin protein cages, [4] [5] while both bacteria and some archaea have gas vesicles. [6] Prokaryotes have simple cell skeletons.
The genetic material is freely found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular. Linear bacterial plasmids have been identified in several species of spirochete bacteria, including members of the genus Borrelia notably Borrelia burgdorferi, which causes Lyme disease. [3]
Most prokaryotes have very little repetitive DNA in their genomes. [32] However, some symbiotic bacteria (e.g. Serratia symbiotica) have reduced genomes and a high fraction of pseudogenes: only ~40% of their DNA encodes proteins. [33] [34] Some bacteria have auxiliary genetic material, also part of their genome, which is carried in plasmids.
One of the major distinctions between bacterial and eukaryotic genetics stems from the bacteria's lack of membrane-bound organelles (this is true of all prokaryotes. While it is a fact that there are prokaryotic organelles, they are never bound by a lipid membrane, but by a shell of proteins), necessitating protein synthesis occur in the cytoplasm.
This is an accepted version of this page This is the latest accepted revision, reviewed on 8 December 2024. DNA molecule containing genetic material of a cell This article is about the DNA molecule. For the genetic algorithm, see Chromosome (genetic algorithm). Chromosome (10 7 - 10 10 bp) DNA Gene (10 3 - 10 6 bp) Function A chromosome and its packaged long strand of DNA unraveled. The DNA's ...
These methods have resulted in novel perspectives on genetic relationships that previously have only been estimated. [5] A significant achievement in the second decade of bacterial genome sequencing was the production of metagenomic data, which covers all DNA present in a sample. Previously, there were only two metagenomic projects published.