episomally

Episomally refers to a state where a circular piece of DNA, such as a plasmid or a viral genome, exists and replicates within a cell independently of the host cell's chromosome. This DNA molecule is not integrated into the host's genome. In bacteria, plasmids often exist episomally, carrying genes that can confer advantages like antibiotic resistance. Many viruses, particularly those that infect eukaryotic cells, also replicate episomally during certain stages of their life cycle. For example, papillomaviruses and Epstein-Barr virus can persist as episomes in the nucleus of infected cells. The replication of episomal DNA is typically managed by the host cell's DNA replication machinery, but the episome possesses its own origin of replication. This independent existence allows for the maintenance and propagation of the genetic material without altering the host's chromosomal structure. However, episomes can be lost during cell division if they are not properly segregated to daughter cells. The term is derived from "episome," which historically described these extrachromosomal genetic elements.