Replicon (genetics)

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A replicon is a DNA molecule or RNA molecule, or a region of DNA or RNA, that replicates from a single origin of replication.

Prokaryotes

For most prokaryotic chromosomes, the replicon is the entire chromosome. One notable exception found comes from archaea, where two Sulfolobus species have been shown to contain three replicons. Examples of bacterial species that have been found to possess multiple replicons include: Rhodobacter sphaeroides (2), Vibrio cholerae,^[1] and Burkholderia multivorans (3). These "secondary" (or tertiary) chromosomes are often described as a molecule that is a mixture between a true chromosome and a plasmid and are sometimes called "chromids". Various Azospirillum species possess 7 replicons, Azospirillum lipoferum, for instance, having 1 bacterial chromosome, 5 chromids, and 1 plasmid.^[2] Plasmids and bacteriophages are usually replicated as single replicons, but large plasmids in Gram-negative bacteria have been shown to carry several replicons.^[3]

Eukaryotes

For eukaryotic chromosomes, there are multiple replicons per chromosome. The definition of replicons is somewhat confused with mitochondria, as they use unidirectional replication with two separate origins.

References

↑ Tagomori, K.; Iida, T.; Honda, T. (2002). "Comparison of genome structures of vibrios, bacteria possessing two chromosomes". Journal of bacteriology 184 (16): 4351–4358. doi:10.1128/JB.184.16.4351-4358.2002. PMC 135242. PMID 12142404.
↑ Wisniewski-Dyé, F.; Borziak, K.; Khalsa-Moyers, G.; Alexandre, G.; Sukharnikov, L. O.; Wuichet, K.; Hurst, G. B.; McDonald, W. H.; Robertson, J. S.; Barbe, V.; Calteau, A.; Rouy, Z.; Mangenot, S.; Prigent-Combaret, C.; Normand, P.; Boyer, M.; Siguier, P.; Dessaux, Y.; Elmerich, C.; Condemine, G.; Krishnen, G.; Kennedy, I.; Paterson, A. H.; González, V.; Mavingui, P.; Zhulin, I. B. (2011). "Azospirillum Genomes Reveal Transition of Bacteria from Aquatic to Terrestrial Environments". In Richardson, Paul M. PLoS Genetics 7 (12): e1002430. doi:10.1371/journal.pgen.1002430. PMC 3245306. PMID 22216014.
↑ Thomas, Christopher M. (2000-05-01). Horizontal Gene Pool: Bacterial Plasmids and Gene Spread (1 ed.). CRC Press. ISBN 9057024624.

DNA replication (comparing Prokaryotic to Eukaryotic)

Initiation

Prokaryotic (initiation)	Pre-replication complex Cdc6 Helicase dnaA dnaB T7 Primase dnaG

Eukaryotic (preparation in G1 phase)	Pre-replication complex Origin recognition complex ORC1 ORC2 ORC3 ORC4 ORC5 ORC6 Cdc6 Cdt1 Minichromosome maintenance MCM2 MCM3 MCM4 MCM5 MCM6 MCM7 Licensing factor Autonomously replicating sequence Single-strand binding protein SSBP2 SSBP3 SSBP4 RNase H RNASEH1 RNASEH2A Helicase: HFM1 Primase: PRIM1 PRIM2

Both	Origin of replication/Ori/Replicon Replication fork Lagging and leading strands Okazaki fragment Primer

Replication

Prokaryotic (elongation)	DNA polymerase III holoenzyme dnaC dnaE dnaH dnaN dnaQ dnaT dnaX holA holB holC holD holE Replisome DNA ligase DNA clamp Topoisomerase DNA gyrase Prokaryotic DNA polymerase: DNA polymerase I Klenow fragment

Eukaryotic (synthesis in S phase)	Replication factor C RFC1 Flap endonuclease FEN1 Topoisomerase Replication protein A RPA1 Eukaryotic DNA polymerase: delta POLD1 POLD2 POLD3 POLD4 DNA clamp PCNA

Both	Movement: Processivity DNA ligase

Termination

Telomere: Telomerase
- TERT
- TERC
- DKC1

See also: DNA replication and repair-deficiency disorder B bsyn: dna (repl, cycl, reco, repr) · tscr (fact, tcrg, nucl, rnat, rept, ptts) · tltn (risu, pttl, nexn) · dnab, rnab/runp · stru (domn, 1°, 2°, 3°, 4°)

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