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(ĕp`ĭsōm), unit of genetic material composed of a series of genesgene,
the structural unit of inheritance in living organisms. A gene is, in essence, a segment of DNA that has a particular purpose, i.e., that codes for (contains the chemical information necessary for the creation of) a specific enzyme or other protein.
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 that sometimes has an independent existence in a host cell and at other times is integrated into a chromosomechromosome
, structural carrier of hereditary characteristics, found in the nucleus of every cell and so named for its readiness to absorb dyes. The term chromosome
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 of the cell, replicating itself along with the chromosome. Episomes have been studied in bacteria. One group of episomes are actually virusesvirus,
parasite with a noncellular structure composed mainly of nucleic acid within a protein coat. Most viruses are too small (100–2,000 Angstrom units) to be seen with the light microscope and thus must be studied by electron microscopes.
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 that infect bacteria. As autonomous units they destroy host cells, and as segments integrated into a chromosome they multiply in cell division and are transferred to daughter cells. Episomes called sex factors determine whether chromosome material will be transferred from one bacterium to another. Other episomes carry genes that make bacteria resistant to the inhibitory action of antibiotics. See recombinationrecombination,
process of "shuffling" of genes by which new combinations can be generated. In recombination through sexual reproduction, the offspring's complete set of genes differs from that of either parent, being rather a combination of genes from both parents.
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The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a genetic factor that can exist in a cell either autonomously (in the cytoplasm) or integrated with the chromosome; a molecule of deoxyribonucleic acid. The genome of the temperate lambda bacteriophage, the sex (or F) factor, and some R factors that transmit drug resistance to bacteria, for example, are episomes.

Episomes are not essential constituents of cells, and they can change from one state to another, depending on the type of cell. In E. coli cells, for example, the genome of the temperate lambda bacteriophage may be either integrated or autonomous, whereas in the cells of the causative agent of typhoid fever it is found only in the autonomous state. Most autonomous episomes behave like typical plasmids. Some researchers regard episomes as a transitional link between the structures that determine chromosomal and nonchromosomal heredity.


Stent, G. Molekuliarnaia genetika. Moscow, 1974. (Translated from English.)
Meynell, G. Bakterial’nve plazmidy. Moscow, 1976. (Translated from English.) ’


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A circular genetic element in bacteria, presumably a deoxyribonucleic acid fragment, which is not necessary for survival of the organism and which can be integrated in the bacterial chromosome or remain free.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
To evaluate the iPSC DNA for the presence of spontaneous integrations of the episomal plasmids used in the generation of the cells, we performed the screening through PCR with two sets of primers designed from sequences pre-established in literature [42] and synthesized for amplification and identification of each one of the vectors used in cell generation.
The following subcloning steps were performed: Construct A, the chimeric gene and stuffer fragment of pPyCAGIP (an episomal vector, kind gift from Professor A.
"You can give rise to iPSCs at a high efficiency rate by using the Epi5 Episomal iPSC Reprogramming Kit," said Dr.
The ISH signal patterns of HPV DNA have been associated with the physical status of HPV in infected cells, that is, episomal or integrated forms.
The urine cells collected from healthy adults were expanded and reprogrammed by two episomal plasmids containing OCT4, SOX2, KLF4, SV40T, and miR-302-367 cluster on feeder-free and serum-free culture conditions, acquired pluripotent features like embryonic stem cells (Figure 1(a)).
HPV integration: HPV in the cervical cells could either be in an episomal state or an integrated state or a mixed state that contains both forms of the virus.
HPV type 16 was highly prevalent ([approximately equal to] 90%) in OSCC in all studies; other HPV types (e.g., HPV-31, -33, -58, -59, -62, and -72) were less common, and HPV was demonstrated to be episomal or integrated into the cellular genome (14,28).
En la etapa no productiva episomal, las celulas basales del epitelio llegan a formar hasta 200 copias con gran amplificacion del genoma.
First, using the cultured skin cells, the team delivered a package of so-called reprogramming factors into the cytoplasm--as opposed to the nucleus, where the cell's genetic material resides--via bits of DNA (episomal vectors) that are serially diluted during cell division after making their special delivery.
"The episomal reprogramming method has been widely adopted for research into therapeutic applications of iPS cell technology," said CDI CEO Bob Palay.