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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 ...
The rate of DNA replication in a living cell was first measured as the rate of phage T4 DNA elongation in phage-infected E. coli. [18] During the period of exponential DNA increase at 37 °C, the rate was 749 nucleotides per second. The mutation rate per base pair per replication during phage T4 DNA synthesis is 1.7 per 10 8. [19]
Multiple DNA polymerases have specialized roles in the DNA replication process. In E. coli, which replicates its entire genome from a single replication fork, the polymerase DNA Pol III is the enzyme primarily responsible for DNA replication and forms a replication complex with extremely high processivity.
Rolling circle replication (RCR) is a process of unidirectional nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA or RNA, such as plasmids, the genomes of bacteriophages, and the circular RNA genome of viroids. Some eukaryotic viruses also replicate their DNA or RNA via the rolling circle mechanism.
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.
A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA.These enzymes are essential for DNA replication and usually work in groups to create two identical DNA duplexes from a single original DNA duplex.
The replication of bacteriophage T4 DNA upon infection of E. coli is a well-studied DNA replication system. During the period of exponential DNA increase at 37°C, the rate of elongation is 749 nucleotides per second. [11] The mutation rate during replication is 1.7 mutations per 10 8 base pairs. [12]