Ori (genetics)

Ori is the DNA sequence that signals for the origin of replication, sometimes referred to simply as origin. In E. coli, ori is some 250 nucleotides in length for the chromosomal origin (oriC). The plasmid ori sequences are similar to oriC, and are called oriV (origin of vegetative replication).

During conjugation, the rolling circle mode of replication starts at the oriT ('T' for transfer) sequence of the FAT plasmid.

Bacteria have a single origin for replication. Eukaryotes have multiple replicons, each with an ori. The replicons range from 40 kb length, in yeast and Drosophila, to 300 kb in plants.

Mitochondrial DNA in many organisms has two ori sequences. In humans, they are called oriH and oriL for the heavy and light strand of the DNA, each is the origin of replication for single-stranded replication.

References

Lewin, Benjamin (2004). Genes VIII. Prentice Hall.

DNA replication (comparing Prokaryotic to Eukaryotic)

Initiation

Prokaryotic (initiation)	Pre-replication complex dnaC 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 fragments 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: alpha POLA1 POLA2 PRIM1 PRIM2 delta POLD1 POLD2 POLD3 POLD4 epsilon POLE POLE2 POLE3 POLE4 DNA clamp PCNA Control of chromosome duplication

Both	Movement: Processivity DNA ligase

Termination

Telomere: Telomerase
- TERT
- TERC
- DKC1

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Ori (genetics)

See also

References