Origin: Anc Greek
επί-/epi(=as a prefix means
1. over, upon, at, towards, during
Literally meaning : additional to body (chromosome)
by Jacob and Wollman in 1961, as a genetic factor that can persist in both the intgrated state and as an extrachromosomal replicon in host cells.
DefinitionAn episome is a portion of genetic material that can exist either autonomously in the cytoplasm or as part of a chromosome, especialy in bacteria. Examples of episomes include insertion sequences and transposons, viruses, and the bacterial sex plasmid F.