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Multiple DNA polymerases take on different roles in the DNA replication process. In E. coli, DNA Pol III is the polymerase enzyme primarily responsible for DNA replication. It assembles into a replication complex at the replication fork that exhibits extremely high processivity, remaining intact for the entire replication cycle.
This mechanism is conserved from prokaryotes to eukaryotes and is known as semiconservative DNA replication. The process of semiconservative replication for the site of DNA replication is a fork-like DNA structure, the replication fork, where the DNA helix is open, or unwound, exposing unpaired DNA nucleotides for recognition and base pairing ...
Prokaryotic DNA Replication is the process by which a prokaryote duplicates its DNA into another copy that is passed on to daughter cells. [1] Although it is often studied in the model organism E. coli, other bacteria show many similarities. [2] Replication is bi-directional and originates at a single origin of replication (OriC). [3]
The process of duplicating DNA is called DNA replication, and it takes place by first unwinding the duplex DNA molecule, starting at many locations called DNA replication origins, followed by an unzipping process that unwinds the DNA as it is being copied. However, replication does not start at all the different origins at once.
MCM2-7 is required for both DNA replication initiation and elongation; its regulation at each stage is a central feature of eukaryotic DNA replication. [3] During G1 phase, the two head-to-head Mcm2-7 rings serve as the scaffold for the assembly of the bidirectional replication initiation complexes at the replication origin.
Before this time, it was commonly thought that replication was a continuous process for both strands, but the discoveries involving E. coli led to a new model of replication. The scientists found there was a discontinuous replication process by pulse-labeling DNA and observing changes that pointed to non-contiguous replication.
During S-phase, the cell converts pre-RCs into active replication forks to initiate DNA replication. [4] This process depends on the kinase activity of Cdc7 and various S-phase CDKs, both of which are upregulated upon S-phase entry. [4] Activation of the pre-RC is a closely regulated and highly sequential process.
During the elongation phase of replication, the enzymes that were assembled at oriC during initiation proceed along each arm of the chromosome, in opposite directions away from the oriC, replicating the DNA to create two identical copies. This process is known as bidirectional replication.